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{{short description|Natural number}}
{{Short description|Integer number 3}}
{{about|the number|the year|AD 3|other uses|3 (disambiguation)|and|III (disambiguation)|and|Number Three (disambiguation)}}
{{Hatnote|This article is about the number. For the years, see [[BC 3]] and [[AD 3]]. For other uses, see [[3 (disambiguation)]], [[III (disambiguation)]] and [[Number Three (disambiguation)]].}}
{{distinguish|Ezh{{!}}Ʒ (ezh)|Yogh{{!}}Ȝ (yogh)|Ze (Cyrillic){{!}}З (ze)}}
{{Distinguish|Ze (Cyrillic){{!}}З (ze)|Ezh{{!}}Ʒ (ezh)|Yogh{{!}}Ȝ (yogh)|ayin{{!}}ع (ʿayn)}}
{{More footnotes needed|date=February 2024}}
{{Hatnote|For [[Wikipedia:Naming conventions (technical restrictions)#Forbidden characters|technical reasons]], ":3" and ":-3" redirect here. For the keyboard symbols, see [[List of emoticons]].}}
{{technical reasons|:3|the keyboard symbols|List of emoticons}}

{{Infobox number
{{Infobox number
|number=3
|number=3
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|lang9=[[Khmer numerals|Khmer]]
|lang9=[[Khmer numerals|Khmer]]
|lang9 symbol={{resize|150%|៣}}
|lang9 symbol={{resize|150%|៣}}
|lang11=[[Malayalam language|Malayalam]]
|lang10=[[Armenian numerals|Armenian]]|lang10 symbol=Գ|lang11=[[Malayalam language|Malayalam]]
|lang11 symbol={{resize|150%|൩}}
|lang11 symbol={{resize|150%|൩}}
|lang12=[[Tamil language|Tamil]]
|lang12=[[Tamil language|Tamil]]
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|lang17=[[Lao numerals|Lao]]
|lang17=[[Lao numerals|Lao]]
|lang17 symbol={{resize|150%|໓}}
|lang17 symbol={{resize|150%|໓}}
|lang18=[[Georgian numerals|Georgian]]
}}
|lang18 symbol={{resize|130%|Ⴂ/ⴂ/გ}} ([[Gani (letter)|Gani]])
'''3''' ('''three''') is a [[number]], [[numeral (linguistics)|numeral]] and [[numerical digit|digit]]. It is the [[natural number]] following [[2]] and preceding [[4]], and is the smallest odd [[prime number]]. It has religious or cultural significance in many societies.
|lang19=[[Babylonian cuneiform numerals|Babylonian numeral]]|lang19 symbol=𒐗|lang20=[[Maya numerals]]|lang20 symbol=•••|lang21=[[Morse code]]|lang21 symbol={{resize|150%|... _ _}}}}

'''3''' ('''three''') is a [[number]], [[numeral (linguistics)|numeral]] and [[numerical digit|digit]]. It is the [[natural number]] following [[2]] and preceding [[4]], and is the smallest odd [[prime number]] and the only prime preceding a square number. It has religious and cultural significance in many societies.


==Evolution of the Arabic digit==
==Evolution of the Arabic digit==
[[File:Evolution3glyph.png|x50px|left]]
The use of three lines to denote the number 3 occurred in many writing systems, including some (like Roman and [[Chinese numerals]]) that are still in use. That was also the original representation of 3 in the [[Brahmic numerals|Brahmic]] (Indian) numerical notation. However, during the [[Gupta Empire]] the sign was modified by the addition of a curve on each line. The [[Nagari]] rotated the lines clockwise{{clarify |date=May 2019 |reason=since didn't state whether lines were originally vertical or horizontal, I'm not sure the detail about rotation makes sense}}, ended each line with a short downward stroke on the right. In cursive, script the three strokes were eventually connected to form a glyph resembling a {{angbr|3}} with an additional stroke at the bottom: '''३'''.
The use of three lines to denote the number 3 occurred in many writing systems, including some (like Roman and [[Chinese numerals]]) that are still in use. That was also the original representation of 3 in the [[Brahmic numerals|Brahmic]] (Indian) numerical notation, its earliest forms aligned vertically.<ref name="Smith Karpinski 1911">{{cite book |last1=Smith |first1=David Eugene |last2=Karpinski |first2=Louis Charles |author1-link=David Eugene Smith |author2-link=Louis Charles Karpinski |title=The Hindu-Arabic numerals |date=1911 |publisher=Ginn and Company |location=Boston; London |pages=27–29, 40–41 |url=https://archive.org/details/hinduarabicnumer00smitrich/}}</ref> However, during the [[Gupta Empire]] the sign was modified by the addition of a curve on each line. The [[Nāgarī script]] rotated the lines clockwise, so they appeared horizontally, and ended each line with a short downward stroke on the right. In cursive script, the three strokes were eventually connected to form a glyph resembling a {{angbr|3}} with an additional stroke at the bottom: '''३'''.


The Indian digits spread to the [[Caliphate]] in the 9th century. The bottom stroke was dropped around the 10th century in the western parts of the Caliphate, such as the [[Maghreb]] and [[Al-Andalus]], when a distinct variant ("Western Arabic") of the digit symbols developed, including modern Western 3. In contrast, the Eastern Arabs retained and enlarged that stroke, rotating the digit once more to yield the modern ("Eastern") [[Arabic script|Arabic]] digit "'''٣'''".<ref>Georges Ifrah, ''The Universal History of Numbers: From Prehistory to the Invention of the Computer'' transl. David Bellos et al. London: The Harvill Press (1998): 393, Fig. 24.63</ref>
The Indian digits spread to the [[Caliphate]] in the 9th century. The bottom stroke was dropped around the 10th century in the western parts of the Caliphate, such as the [[Maghreb]] and [[Al-Andalus]], when a distinct variant ("Western Arabic") of the digit symbols developed, including modern Western 3. In contrast, the Eastern Arabs retained and enlarged that stroke, rotating the digit once more to yield the modern ("Eastern") [[Arabic script|Arabic]] digit "'''٣'''".<ref>Georges Ifrah, ''The Universal History of Numbers: From Prehistory to the Invention of the Computer'' transl. David Bellos et al. London: The Harvill Press (1998): 393, Fig. 24.63</ref>


In most modern Western [[typeface]]s, the digit 3, like the other [[decimal digit]]s, has the height of a [[capital letter]], and sits on the [[baseline (typography)|baseline]]. In typefaces with [[text figures]], on the other hand, the glyph usually has the height of a [[lowercase letter]] "x" and a [[descender]]: "[[File:Text figures 036.svg|50px]]". In some [[French language|French]] text-figure typefaces, though, it has an [[ascender (typography)|ascender]] instead of a descender.
[[File:Text_figures.jpg|thumb|Text figures in various fonts: Adobe Garamond, Adobe Caslon, Theano Didot and Essonnes Text]]
In most modern Western [[typeface]]s, the digit 3, like the other [[decimal digit]]s, has the height of a [[capital letter]], and sits on the [[baseline (typography)|baseline]]. In typefaces with [[text figures]], on the other hand, the glyph usually has the height of a [[lowercase letter]] "x" and a [[descender]]: "[[File:Text figures 036.svg|30px]]". In some [[French language|French]] text-figure typefaces, though, it has an [[ascender (typography)|ascender]] instead of a descender.


{{anchor|Flat-topped 3}}
{{anchor|Flat-topped 3}}
A common graphic variant of the digit three has a flat top, similar to the letter [[Ʒ]] (ezh). This form is sometimes used to obstruct changing a three into an eight with fraudulent intent. It is found on [[Universal Product Code|UPC-A]] barcodes and [[standard 52-card deck]]s.
A common graphic variant of the digit three has a flat top, similar to the letter [[Ʒ]] (ezh). This form is sometimes used to prevent falsifying a 3 as an 8. It is found on [[Universal Product Code|UPC-A]] barcodes and [[standard 52-card deck]]s.


==Mathematics==
== Mathematics ==
According to [[Pythagoras]] and the [[Pythagoreanism|Pythagorean]] school, the number 3, which they called ''triad'', is the only number to equal the sum of all the terms below it, and the only number whose sum with those below equals the product of them and itself.<ref>{{citation |author=Priya Hemenway |title=Divine Proportion: Phi In Art, Nature, and Science |pages=53–54 |year=2005 |publisher=Sterling Publishing Company Inc. |isbn=1-4027-3522-7}}</ref>
'''3''' is:
*a rough approximation of [[pi|{{pi}}]] (3.1415...) and a very rough approximation of [[E (mathematical constant)|''e'']] (2.71828..) when doing quick estimates.
*the number of non-collinear points needed to determine a [[Plane (mathematics)|plane]] and a [[circle]].
*the first odd [[prime number]] and the second smallest prime.
*the first [[Fermat prime]] ({{nowrap|2{{sup|2{{sup|''n''}}}} + 1}}).
*the first [[Mersenne prime]] ({{nowrap|2{{sup|''n''}} − 1}}).
*the second [[Sophie Germain prime]].
*the second Mersenne prime exponent.
*the second [[factorial prime]] ({{nowrap|2! + 1}}).
*the second [[Lucas prime]].
*the second [[triangular number]]. It is the only prime triangular number.
*the fourth [[Fibonacci number]].
*the smallest number of sides that a simple (non-self-intersecting) [[polygon]] can have.

Three is the only prime which is one less than a [[square number|perfect square]]. Any other number which is {{nowrap|''n''{{sup|2}} − 1}} for some integer ''n'' is not prime, since it is {{nowrap|(''n'' − 1)(''n'' + 1)}}. This is true for 3 as well (with {{nowrap|''n'' {{=}} 2}}), but in this case the smaller factor is 1. If ''n'' is greater than 2, both {{nowrap|''n'' − 1}} and {{nowrap|''n'' + 1}} are greater than 1 so their product is not prime.


=== Divisibility rule ===
A [[natural number]] is [[divisible]] by three if the [[digital root|sum of its digits]] in [[base 10]] is divisible by 3. For example, the number 21 is divisible by three (3 times 7) and the sum of its digits is 2 + 1 = 3. Because of this, the reverse of any number that is divisible by three (or indeed, any [[permutation]] of its digits) is also divisible by three. For instance, 1368 and its reverse 8631 are both divisible by three (and so are 1386, 3168, 3186, 3618, etc.). See also [[Divisibility rule]]. This works in [[base 10]] and in any [[positional notation|positional numeral system]] whose [[radix|base]] divided by three leaves a remainder of one (bases 4, 7, 10, etc.).
A [[natural number]] is [[divisible]] by three if the [[digital root|sum of its digits]] in [[base 10]] is divisible by 3. For example, the number 21 is divisible by three (3 times 7) and the sum of its digits is 2 + 1 = 3. Because of this, the reverse of any number that is divisible by three (or indeed, any [[permutation]] of its digits) is also divisible by three. For instance, 1368 and its reverse 8631 are both divisible by three (and so are 1386, 3168, 3186, 3618, etc.). See also [[Divisibility rule]]. This works in [[base 10]] and in any [[positional notation|positional numeral system]] whose [[radix|base]] divided by three leaves a remainder of one (bases 4, 7, 10, etc.).


=== Properties of the number ===
Three of the five [[Platonic solids]] have triangular faces – the [[tetrahedron]], the [[octahedron]], and the [[icosahedron]]. Also, three of the five Platonic solids have [[vertex (geometry)|vertices]] where three faces meet&nbsp;– the [[tetrahedron]], the [[hexahedron]] ([[cube]]), and the [[dodecahedron]]. Furthermore, only three different types of [[polygons]] comprise the faces of the five Platonic solids&nbsp;– the [[triangle]], the [[square]], and the [[pentagon]].
3 is the second smallest [[prime number]] and the first [[Parity (mathematics)|odd]] prime number. It is the first [[unique prime]], such that the [[period length]] value of [[1]] of the [[decimal expansion]] of its [[Multiplicative inverse|reciprocal]], 0.333..., is unique. 3 is a [[twin prime]] with [[5]], and a [[cousin prime]] with [[7]], and the only known number <math>n</math> such that <math>n</math>! − 1 and <math>n</math>! + 1 are prime, as well as the only prime number <math>p</math> such that <math>p</math> − 1 yields another prime number, [[2]]. A [[triangle]] is made of three [[Edge (geometry)|sides]]. It is the smallest non-self-intersecting [[polygon]] and the only polygon not to have proper [[diagonals]]. When doing quick estimates, 3 is a rough approximation of [[pi|{{pi}}]], 3.1415..., and a very rough approximation of [[E (mathematical constant)|''e'']], 2.71828...


3 is the first [[Mersenne prime]], as well as the second Mersenne prime exponent and the second [[Double Mersenne number#Double Mersenne primes|double Mersenne prime exponent]], for 7 and [[127 (number)|127]], respectively. 3 is also the first of five known [[Fermat prime]]s, which include 5, [[17 (number)|17]], [[257 (number)|257]], and [[65537 (number)|65537]]. It is the second [[Fibonacci number|Fibonacci prime]] (and the second [[Lucas prime]]), the second [[Sophie Germain prime]], the third Harshad number in base 10, and the second [[factorial prime]], as it is equal to 2! + 1.
There are only three distinct 4×4 [[panmagic square]]s.


3 is the second and only prime [[triangular number]], and [[Gauss]] proved that every integer is the sum of at most 3 [[triangular numbers]].
According to [[Pythagoras]] and the [[Pythagoreanism|Pythagorean]] school, the number 3, which they called ''triad'', is the noblest of all digits, as it is the only number to equal the sum of all the terms below it, and the only number whose sum with those below equals the product of them and itself.<ref>{{citation |author=Priya Hemenway |title=Divine Proportion: Phi In Art, Nature, and Science |publisher=Sterling Publishing Company Inc. |year=2005 |isbn=1-4027-3522-7 |pages=53–54}}</ref>


Three is the only prime which is one less than a [[square number|perfect square]]. Any other number which is <math>n^2</math> − 1 for some integer <math>n</math> is not prime, since it is (<math>n</math> − 1)(<math>n</math> + 1). This is true for 3 as well (with <math>n</math> = 2), but in this case the smaller factor is 1. If <math>n</math> is greater than 2, both <math>n</math> − 1 and <math>n</math> + 1 are greater than 1 so their product is not prime.

=== Related properties ===
The [[trisection of the angle]] was one of the three famous problems of antiquity.
The [[trisection of the angle]] was one of the three famous problems of antiquity.


3 is the number of non-collinear points needed to determine a [[Plane (mathematics)|plane]], a [[circle]], and a [[parabola]].
[[Gauss]] proved that every integer is the sum of at most 3 [[triangular numbers]].

There are only three distinct 4×4 [[panmagic square]]s.

Three of the five [[Platonic solids]] have triangular faces – the [[tetrahedron]], the [[octahedron]], and the [[icosahedron]]. Also, three of the five Platonic solids have [[vertex (geometry)|vertices]] where three faces meet&nbsp;– the [[tetrahedron]], the [[hexahedron]] ([[cube]]), and the [[dodecahedron]]. Furthermore, only three different types of [[polygons]] comprise the faces of the five Platonic solids&nbsp;– the [[triangle]], the [[square]], and the [[pentagon]].

There are three finite convex [[Uniform polyhedron|uniform polytope groups]] in three dimensions, aside from the infinite families of [[Prism (geometry)|prisms]] and [[antiprisms]]: the [[tetrahedral group]], the [[octahedral group]], and the [[icosahedral group]]. In dimensions <math>n</math> ⩾ 5, there are only three regular polytopes: the <math>n</math>-[[simplex]]es, <math>n</math>-[[cube]]s, and <math>n</math>-[[orthoplex]]es. In dimensions <math>n</math> ⩾ [[9]], the only three uniform polytope families, aside from the numerous infinite [[proprism]]atic families, are the <math>\mathrm{A}_{n}</math> simplex, <math>\mathrm{B}_{n}</math> cubic, and <math>\mathrm{D}_{n}</math> [[Demihypercube|demihypercubic]] families. For [[Coxeter–Dynkin diagram#Paracompact (Koszul simplex groups)|paracompact hyperbolic honeycomb]]s, there are three groups in [[dimension]]s [[Uniform 7-polytope#Regular and uniform hyperbolic honeycombs|6]] and [[Uniform 10-polytope#Regular and uniform hyperbolic honeycombs|9]], or equivalently of ranks 7 and 10, with no other forms in higher dimensions. Of the final three groups, the largest and most important is [[E9 honeycomb|<math>{\bar{T}}_9</math>]], that is associated with an important [[En (Lie algebra)|Kac–Moody]] [[Lie algebra]] <math>\mathrm {E}_{10}</math>.<ref>{{Cite journal |last1=Allcock |first1=Daniel |date=May 2018 |title=Prenilpotent Pairs in the E10 root lattice. |url=https://web.ma.utexas.edu/users/allcock/research/prenilpotent.pdf |url-status=live |journal=Mathematical Proceedings of the Cambridge Philosophical Society |volume=164 |issue=3 |pages=473–483 |bibcode=2018MPCPS.164..473A |doi=10.1017/S0305004117000287 |s2cid=8547735 |archive-url=https://web.archive.org/web/20221103135851/https://web.ma.utexas.edu/users/allcock/research/prenilpotent.pdf |archive-date=2022-11-03 |access-date=2022-11-03}}

: "The details of the previous section were E10-specific, but the same philosophy looks likely to apply to the other symmetrizable hyperbolic root systems...it seems valuable to give an outline of how the calculations would go", regarding E10 as a model example of symmetrizability of other root hyperbolic E<sub>n</sub> systems.</ref>


===Numeral systems===
=== Numeral systems ===
There is some evidence to suggest that early man may have used counting systems which consisted of "One, Two, Three" and thereafter "Many" to describe counting limits. Early peoples had a word to describe the quantities of one, two, and three but any quantity beyond was simply denoted as "Many". This is most likely based on the prevalence of this phenomenon among people in such disparate regions as the deep Amazon and Borneo jungles, where western civilization's explorers have historical records of their first encounters with these indigenous people.<ref>{{cite book | last1 = Gribbin | first1 = Mary | last2 = Gribbin | first2 = John R. | last3 = Edney | first3 = Ralph | last4 = Halliday | first4 = Nicholas | title = Big numbers | publisher = Wizard | location = Cambridge | year = 2003 | isbn = 1840464313 }}</ref>
There is some evidence to suggest that early man may have used counting systems which consisted of "One, Two, Three" and thereafter "Many" to describe counting limits. Early peoples had a word to describe the quantities of one, two, and three but any quantity beyond was simply denoted as "Many". This is most likely based on the prevalence of this phenomenon among people in such disparate regions as the deep Amazon and Borneo jungles, where western civilization's explorers have historical records of their first encounters with these indigenous people.<ref>{{cite book | last1 = Gribbin | first1 = Mary | last2 = Gribbin | first2 = John R. | last3 = Edney | first3 = Ralph | last4 = Halliday | first4 = Nicholas | title = Big numbers | publisher = Wizard | location = Cambridge | year = 2003 | isbn = 1840464313 }}</ref>


===List of basic calculations===
=== List of basic calculations ===
{|class="wikitable" style="text-align: center; background: white"
{|class="wikitable" style="text-align: center; background: white"
|-
|-
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==Science==
==Science==
*The Roman numeral III stands for [[giant star]] in the [[stellar classification|Yerkes spectral classification scheme]].
*Three is the [[atomic number]] of [[lithium]].
*Three is the [[atomic number]] of [[lithium]].
*Three is the number of [[Dimension (mathematics and physics)|dimensions]] that humans can perceive. Humans perceive the [[universe]] to have [[Three-dimensional space|three spatial dimensions]], but some theories, such as [[string theory]], suggest there are more.{{citation needed|date=January 2024}}
*Three is the [[ASCII]] code of "[[End-of-text character|End of Text]]".
*Three is the number of elementary fermion [[Generation (particle physics)|generations]] according to the [[Standard Model]] of particle physics.<ref>
*Three is the number of [[Dimension (mathematics and physics)|dimensions]] that humans can perceive. Humans perceive the [[universe]] to have [[Three-dimensional space|three spatial]] [[dimensions]], but some theories, such as [[string theory]], suggest there are more.
{{cite conference
*Three is the number of elementary fermion [[Generation (particle physics)|generations]] according to the [[Standard Model]] of particle physics.
|last = Harari |first = H.
*The [[triangle]], a [[polygon]] with three [[Edge (geometry)|edges]] and three [[Vertex (geometry)|vertices]], is the most stable physical shape. For this reason it is widely utilized in construction, engineering and design.<ref>"[https://web.archive.org/web/20120412203618/http://www.mathsinthecity.com/sites/most-stable-shape-triangle Most stable shape- triangle]". ''Maths in the city''. Retrieved February 23, 2015.</ref>
|year = 1977
*The ability of the [[human eye]] to distinguish [[color]]s is based upon the varying sensitivity of different cells in the [[retina]] to light of different [[wavelengths]]. Humans being [[Trichromacy|trichromatic]], the retina contains three types of color receptor cells, or [[cone cell|cones]].
|title = Three generations of quarks and leptons
|book-title = Proceedings of the XII Rencontre de Moriond
|editor1 = van Goeler, E.
|editor2 = Weinstein, R.
|page = 170
|id = SLAC-PUB-1974
|url = http://slac.stanford.edu/cgi-wrap/getdoc/slac-pub-1974.pdf
}}
</ref>
*In [[particle physics]], each [[proton]] or [[neutron]] is composed of three [[quarks]].<ref>
{{cite book
|author=Adair, R.K.
|year=1989
|title=The Great Design: Particles, Fields, and Creation
|page=214
|publisher=[[Oxford University Press]]
|bibcode=1988gdpf.book.....A
}}</ref>
*There are three [[primary color]]s in the [[additive color|additive]] and [[subtractive color|subtractive]] models.
*There are three [[primary color]]s in the [[additive color|additive]] and [[subtractive color|subtractive]] models.
*The ability of the [[human eye]] to distinguish [[color]]s is based upon the varying sensitivity of different cells in the [[retina]] to light of different [[wavelengths]]. Humans being [[Trichromacy|trichromatic]], the retina contains three types of color receptor cells, or [[cone cell|cones]].{{citation needed|date=January 2024}}
*In [[physics]], [[three-body problem|three-body problems]] have no general [[closed-form solution]], unlike [[two-body problem|two-body problems]].<ref>{{cite encyclopedia
| last = Barrow-Green
| first = June
| year = 2008
| title = The Three-Body Problem
| editor-last1 = Gowers
| editor-first1 = Timothy
| editor-last2 = Barrow-Green
| editor-first2 = June
| editor-last3 = Leader
| editor-first3 = Imre
| encyclopedia = The Princeton Companion to Mathematics
| pages = 726–728
| publisher = Princeton University Press
}}</ref>


==Engineering==
===[[Protoscience]]===
*The [[triangle]], a [[polygon]] with three [[Edge (geometry)|edges]] and three [[Vertex (geometry)|vertices]], is the most stable physical shape. For this reason it is widely utilized in construction, engineering and design.<ref>"[https://web.archive.org/web/20120412203618/http://www.mathsinthecity.com/sites/most-stable-shape-triangle Most stable shape- triangle]". ''Maths in the city''. Retrieved February 23, 2015.</ref>
*In European [[alchemy]], the three primes ({{lang-la|tria prima}}) were [[salt (chemistry)|salt]] ([[File:Line within circle.svg|20px]]), [[sulfur]] ([[Image:Sulphur.svg|10px]]) and [[mercury (element)|mercury]] ([[Image:Mercury symbol.svg|15px]]).<ref name="Eric John Holmyard 1990. p.153">Eric John Holmyard. ''Alchemy.'' 1995. p.153</ref><ref>Walter J. Friedlander. ''The golden wand of medicine: a history of the caduceus symbol in medicine.'' 1992. p.76-77</ref>

*The three [[doshas]] (weaknesses) and their [[antidote]]s are the basis of [[Ayurvedic medicine]] in India.
===Protoscience===
*In European [[alchemy]], the three primes ({{lang-la|tria prima}}) were [[salt (chemistry)|salt]] ([[File:Salt symbol (alchemical).svg|16px]]), [[sulfur]] ([[Image:Sulphur symbol (fixed width).svg|16px]]) and [[mercury (element)|mercury]] ([[Image:Mercury symbol (fixed width).svg|16px]]).<ref name="Eric John Holmyard 1990. p.153">Eric John Holmyard. ''Alchemy.'' 1995. p.153</ref><ref>Walter J. Friedlander. ''The golden wand of medicine: a history of the caduceus symbol in medicine.'' 1992. p.76-77</ref>
*The three [[doshas]] (weaknesses) and their [[antidote]]s are the basis of [[Ayurvedic medicine]] in India.{{citation needed|date=October 2023}}


===Pseudoscience===
===Pseudoscience===
*Three is the symbolic representation for [[Mu (lost continent)|Mu]], [[Augustus Le Plongeon]]'s and [[James Churchward]]'s lost continent.<ref name="Three is for the Lost Continent of Mu">{{cite web |url=http://www.bibliotecapleyades.net/atlantida_mu/contmu/contmu09.htm |title=The Lost Continent of Mu – Symbols, Vignettes, Tableaux and Diagrams |first=James |last=Churchward |year=1931 |access-date=2016-03-15 |work=Biblioteca Pleyades}}</ref>
*Three is the symbolic representation for [[Mu (lost continent)|Mu]], [[Augustus Le Plongeon]]'s and [[James Churchward]]'s lost continent.<ref name="Three is for the Lost Continent of Mu">{{cite web |url=http://www.bibliotecapleyades.net/atlantida_mu/contmu/contmu09.htm |title=The Lost Continent of Mu – Symbols, Vignettes, Tableaux and Diagrams |first=James |last=Churchward |year=1931 |access-date=2016-03-15 |work=Biblioteca Pleyades |archive-date=2015-07-18 |archive-url=https://web.archive.org/web/20150718115213/http://www.bibliotecapleyades.net/atlantida_mu/contmu/contmu09.htm |url-status=live }}</ref>


==Philosophy==
==Philosophy==
{{Main article|Trichotomy (philosophy)}}
{{Main article|Trichotomy (philosophy)}}
*Philosophers such as [[Aquinas]], [[Immanuel Kant|Kant]], [[Hegel]], [[Charles Sanders Peirce|C.&nbsp;S. Peirce]], and [[Karl Popper]] have made threefold divisions, or ''[[Trichotomy (philosophy)|trichotomies]]'', which have been important in their work.
*Philosophers such as [[Aquinas]], [[Immanuel Kant|Kant]], [[Hegel]], [[Charles Sanders Peirce|C.&nbsp;S. Peirce]], and [[Karl Popper]] have made threefold divisions, or ''[[Trichotomy (philosophy)|trichotomies]]'', which have been important in their work.{{citation needed|date=October 2023}}
*[[Hegel]]'s [[Dialectic#Hegelian dialectics|dialectic]] of [[Thesis, antithesis, synthesis|Thesis + Antithesis = Synthesis]] creates three-ness from two-ness.
*[[Hegel]]'s [[Dialectic#Hegelian dialectic|dialectic]] of [[Thesis, antithesis, synthesis|Thesis + Antithesis = Synthesis]] creates three-ness from two-ness.{{citation needed|date=October 2023}}


==Religion==
==Religion==
{{prose|section|date=October 2023}}{{more references|section|date=October 2023}}
{{See also|Triple deity}}
{{See also|Triple deity}}
[[File:Triple-Goddess-Waxing-Full-Waning-Symbol.svg|thumb|right|Symbol of the Triple Goddess showing the waxing, full and waning Moon]]
Many world religions contain triple deities or concepts of trinity, including:

*the [[Hindu]] [[Trimurti]]
Many world religions contain triple deities or concepts of trinity, including the [[Hindu]] [[Trimurti]] and [[Tridevi]], the [[Triglav (mythology)|Triglav]] (lit. "Three-headed one"), the chief god of the [[slav]]s, the [[three Jewels]] of [[Buddhism]], the [[three Pure Ones]] of [[Taoism]], the [[Christianity|Christian]] [[Trinity|Holy Trinity]], and the [[Triple Goddess (Neopaganism)|Triple Goddess]] of [[Wicca]].
*the Hindu [[Tridevi]]
*the [[Three Jewels]] of [[Buddhism]]
*the [[Three Pure Ones]] of [[Taoism]]
*the [[Christianity|Christian]] [[Trinity|Holy Trinity]]
*the [[Triple Goddess (Neopaganism)|Triple Goddess]] of [[Wicca]]


[[File:Shield-Trinity-Scutum-Fidei-English.svg|thumb|The [[Shield of the Trinity]] is a diagram of the Christian doctrine of the Trinity]]
[[File:Shield-Trinity-Scutum-Fidei-English.svg|thumb|The [[Shield of the Trinity]] is a diagram of the Christian doctrine of the Trinity.]]


===Christianity===
===Christianity===
*The [[threefold office]] of Christ is a Christian doctrine which states that Christ performs the functions of [[prophet]], [[priest]], and [[Christ the king|king]].
*The [[threefold office]] of [[Christ]] is a Christian doctrine which states that Christ performs the functions of [[prophet]], [[priest]], and [[Christ the king|king]].
*The [[ministry of Jesus]] lasted approximately three years.<ref>{{Cite journal |title=HUG 31, ff. 017r-v, inc. CF ad CE = CF ad CV |journal=Codices Hugeniani Online |doi = 10.1163/2468-0303-cohu_31-015}}</ref>
*During the [[Agony in the Garden]], Christ asked three times for the cup to be taken from him.
*During the [[Agony in the Garden]], Christ asked three times for the cup to be taken from him.
*Jesus [[Resurrection of Jesus|rose from the dead]] on the third day after his death.
*Jesus [[Resurrection of Jesus|rose from the dead]] on the third day after his death.
*The [[Temptation of Christ|devil tempted Jesus]] three times.
*The [[Temptation of Christ|devil tempted Jesus]] three times.
*[[Saint Peter]] [[Denial of Peter|thrice denied Jesus]] and [[Restoration of Peter|thrice affirmed his faith in Jesus]].
*[[Saint Peter]] [[Denial of Peter|thrice denied Jesus]] and [[Restoration of Peter|thrice affirmed his faith in Jesus]].
*The [[Biblical magi|Magi]] – wise men who were astronomers/astrologers from Persia{{citation needed|date=May 2016}} – gave Jesus three gifts.<ref>{{Cite journal |title=Encyclopaedia Britannica |doi=10.1163/9789004337862_lgbo_com_050367 |journal=Lexikon des gesamten Buchwesens Online |language=de}}</ref><ref>{{Cite journal |title=The Encyclopaedia Britannica |journal=Nature |url=https://zenodo.org/record/1609149 |date=25 January 1877 |author=T. E. T. |volume=XV |issue=378 |pages=269–271}}</ref>
*The [[Biblical magi|Magi]] – wise men who were astronomers/astrologers from Persia{{citation needed|date=May 2016}} – gave Jesus three gifts.<ref>{{Cite journal |title=Encyclopaedia Britannica |doi=10.1163/9789004337862_lgbo_com_050367 |journal=Lexikon des Gesamten Buchwesens Online |language=de}}</ref><ref>{{Cite journal |title=The Encyclopaedia Britannica |journal=Nature |url=https://zenodo.org/record/1609149 |date=25 January 1877 |author=T. E. T. |volume=XV |issue=378 |pages=269–271 |access-date=12 July 2019 |archive-date=24 July 2020 |archive-url=https://web.archive.org/web/20200724194916/https://zenodo.org/record/1609149 |url-status=live }}</ref>
*There are three [[Synoptic Gospels]] and three [[epistles of John]].
*There are three [[Synoptic Gospels]] and three [[epistles of John]].
*[[Paul the Apostle]] went blind for three days after his [[Conversion of Paul the Apostle|conversion to Christianity]].
*[[Paul the Apostle]] went blind for three days after his [[Conversion of Paul the Apostle|conversion to Christianity]].
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*The prophet [[Balaam]] beat his donkey three times.
*The prophet [[Balaam]] beat his donkey three times.
*The prophet [[Jonah]] spent three days and nights in the belly of a large fish
*The prophet [[Jonah]] spent three days and nights in the belly of a large fish
*Three divisions of the Written [[Torah]]: [[Torah]] (Five Book of Moses), [[Nevi'im]] (Prophets), [[Ketuvim]] (Writings)<ref name=why>{{cite web |url=http://www.askmoses.com/en/article/228,503/Why-are-many-things-in-Judaism-done-three-times.html |title=Why are many things in Judaism done three times? |first=Rabbi Yossi |last=Marcus |year=2015 |access-date=16 March 2015 |work=Ask Moses}}</ref>
*Three divisions of the Written [[Torah]]: [[Torah]] (Five Books of Moses), [[Nevi'im]] (Prophets), [[Ketuvim]] (Writings)<ref name=why>{{cite web |url=http://www.askmoses.com/en/article/228,503/Why-are-many-things-in-Judaism-done-three-times.html |title=Why are many things in Judaism done three times? |first=Rabbi Yossi |last=Marcus |year=2015 |access-date=16 March 2015 |work=Ask Moses |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402134737/http://www.askmoses.com/en/article/228,503/Why-are-many-things-in-Judaism-done-three-times.html |url-status=dead }}</ref>
*Three divisions of the Jewish people: [[Kohen]], [[Levite]], Yisrael
*Three divisions of the Jewish people: [[Kohen]], [[Levite]], Yisrael
*Three daily [[Jewish prayer|prayers]]: ''[[Shacharit]]'', ''[[Mincha]]'', ''[[Maariv]]''
*Three daily [[Jewish prayer|prayers]]: ''[[Shacharit]]'', ''[[Mincha]]'', ''[[Maariv]]''
*Three [[Shabbat]] meals
*Three [[Shabbat]] meals
*Shabbat ends when three stars are visible in the night sky<ref>{{cite web |url=http://www.jewfaq.org/shabbat.htm |title=Shabbat |work=Judaism 101 |year=2011 |access-date=16 March 2015}}</ref>
*Shabbat ends when three stars are visible in the night sky<ref>{{cite web |url=http://www.jewfaq.org/shabbat.htm |title=Shabbat |work=Judaism 101 |year=2011 |access-date=16 March 2015 |archive-date=29 June 2009 |archive-url=https://web.archive.org/web/20090629025034/http://www.jewfaq.org/shabbat.htm |url-status=live }}</ref>
*[[Three Pilgrimage Festivals]]: [[Passover]], [[Shavuot]], [[Sukkot]]
*[[Three Pilgrimage Festivals]]: [[Passover]], [[Shavuot]], [[Sukkot]]
*Three [[matzo]]s on the [[Passover Seder]] table<ref>{{cite web |url=http://www.chabad.org/holidays/passover/pesach_cdo/aid/1702/jewish/The-Three-Matzot.htm |title=The Three Matzot |first=Eliyahu |last=Kitov |author-link=Eliyahu Kitov |year=2015 |work=Chabad.org |access-date=16 March 2015}}</ref>
*Three [[Matzah|matzo]]s on the [[Passover Seder]] table<ref>{{cite web |url=http://www.chabad.org/holidays/passover/pesach_cdo/aid/1702/jewish/The-Three-Matzot.htm |title=The Three Matzot |first=Eliyahu |last=Kitov |author-link=Eliyahu Kitov |year=2015 |work=Chabad.org |access-date=16 March 2015 |archive-date=24 March 2015 |archive-url=https://web.archive.org/web/20150324124011/http://www.chabad.org/holidays/passover/pesach_cdo/aid/1702/jewish/The-Three-Matzot.htm |url-status=live }}</ref>
*[[The Three Weeks]], a period of mourning bridging the fast days of [[Seventeenth of Tammuz]] and [[Tisha B'Av]]
*[[The Three Weeks]], a period of mourning bridging the fast days of [[Seventeenth of Tammuz]] and [[Tisha B'Av]]
*Three cardinal sins for which a Jew must die rather than transgress: [[Idolatry#Judaism|idolatry]], [[murder]], [[Immorality#Sexual immorality|sexual immorality]]<ref>{{cite web |url=http://www.aish.com/jl/m/pm/48936542.html |title=Judaism and Martyrdom |first=Rabbi Aryeh |last=Kaplan |author-link=Aryeh Kaplan |date=28 August 2004 |access-date=16 March 2015 |publisher=Aish.com}}</ref>
*Three cardinal sins for which a Jew must die rather than transgress: [[Idolatry#Judaism|idolatry]], [[murder]], [[Immorality#Sexual immorality|sexual immorality]]<ref>{{cite web |url=http://www.aish.com/jl/m/pm/48936542.html |title=Judaism and Martyrdom |first=Rabbi Aryeh |last=Kaplan |author-link=Aryeh Kaplan |date=28 August 2004 |access-date=16 March 2015 |publisher=Aish.com |archive-date=20 March 2015 |archive-url=https://web.archive.org/web/20150320081912/http://www.aish.com/jl/m/pm/48936542.html |url-status=live }}</ref>
*[[Upsherin]], a Jewish boy's first haircut at age 3<ref>{{cite web |url=http://www.chabad.org/library/article_cdo/aid/710724/jewish/The-Basics-of-the-Upsherin.htm |title=The Basics of the Upsherin: A Boy's First Haircut |year=2015 |access-date=16 March 2015 |work=Chabad.org}}</ref>
*[[Upsherin]], a Jewish boy's first haircut at age 3<ref>{{cite web |url=http://www.chabad.org/library/article_cdo/aid/710724/jewish/The-Basics-of-the-Upsherin.htm |title=The Basics of the Upsherin: A Boy's First Haircut |year=2015 |access-date=16 March 2015 |work=Chabad.org |archive-date=22 March 2015 |archive-url=https://web.archive.org/web/20150322124639/http://www.chabad.org/library/article_cdo/aid/710724/jewish/The-Basics-of-the-Upsherin.htm |url-status=live }}</ref>
*A [[Beth din]] is composed of three members
*A [[Beth din]] is composed of three members
*Potential [[Conversion to Judaism|converts]] are traditionally turned away three times to test their sincerity<ref>{{cite web |url=http://www.convert.org/Conversion_Process.html |title=The Conversion Process |publisher=Center for Conversion to Judaism |access-date=16 March 2015}}</ref>
*Potential [[Conversion to Judaism|converts]] are traditionally turned away three times to test their sincerity<ref>{{cite web |url=http://www.convert.org/Conversion_Process.html |title=The Conversion Process |publisher=Center for Conversion to Judaism |access-date=16 March 2015 |archive-date=23 February 2021 |archive-url=https://web.archive.org/web/20210223162821/http://www.convert.org/Conversion_Process.html |url-status=live }}</ref>
*In the [[Jewish mysticism|Jewish mystical]] tradition of the [[Kabbalah]], it is believed that [[the soul]] consists of three parts, with the highest being ''[[Soul#Judaism|neshamah]]'' ("breath"), the middle being ''[[ruach]]'' ("wind" or "spirit") and the lowest being ''[[Nephesh|nefesh]]'' ("repose").<ref>Kaplan, Aryeh. "[http://www.aish.com/jl/sp/bas/48942091.html The Soul]". ''Aish''. From ''The Handbook of Jewish Thought'' (Vol. 2, ''Maznaim Publishing''. Reprinted with permission.) September 4, 2004. Retrieved February 24, 2015.</ref> Sometimes the two elements of ''Chayah'' ("life" or "animal") and ''Yechidah'' ("unit") are additionally mentioned.
*In the [[Jewish mysticism|Jewish mystical]] tradition of the [[Kabbalah]], it is believed that [[the soul]] consists of three parts, with the highest being ''[[Soul#Judaism|neshamah]]'' ("breath"), the middle being ''[[ruach]]'' ("wind" or "spirit") and the lowest being ''[[Nephesh|nefesh]]'' ("repose").<ref>Kaplan, Aryeh. "[http://www.aish.com/jl/sp/bas/48942091.html The Soul] {{Webarchive|url=https://web.archive.org/web/20150224124738/http://www.aish.com/jl/sp/bas/48942091.html |date=2015-02-24 }}". ''Aish''. From ''The Handbook of Jewish Thought'' (Vol. 2, ''Maznaim Publishing''. Reprinted with permission.) September 4, 2004. Retrieved February 24, 2015.</ref> Sometimes the two elements of ''Chayah'' ("life" or "animal") and ''Yechidah'' ("unit") are additionally mentioned.
*In the Kabbalah, the [[Tree of life (Kabbalah)|Tree of Life]] (Hebrew: ''Etz ha-Chayim'', עץ החיים) refers to a latter 3-pillar diagrammatic representation of its central mystical symbol, known as the ''[[Sephirot|10 Sephirot]]''.
*In the Kabbalah, the [[Tree of life (Kabbalah)|Tree of Life]] (Hebrew: ''Etz ha-Chayim'', עץ החיים) refers to a latter 3-pillar diagrammatic representation of its central mystical symbol, known as the ''[[Sephirot|10 Sephirot]]''.

===Islam===
*The three core principles in Shia tradition: Tawhid (Oneness of God), Nabuwwa (Concept of Prophethood), Imama (Concept of Imam)


===Buddhism===
===Buddhism===
*The Triple [[Bodhi]] (ways to understand the end of birth) are Budhu, Pasebudhu, and Mahaarahath.
*The Triple [[Bodhi]] (ways to understand the end of birth) are Budhu, Pasebudhu, and Mahaarahath.
*The [[Three Jewels]], the three things that Buddhists take [[Refuge (Buddhism)|refuge]] in.
*The [[Three Jewels]], the three things that Buddhists take refuge in.


===Shinto===
===Shinto===
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*The [[Three Treasures (Taoism)|Three Treasures]] ({{zh|c=[[Wikt:三|三]][[Wikt:寶|寶]]|p=''sānbǎo''| w=''san-pao''}}), the basic [[virtues]] in [[Taoism]].
*The [[Three Treasures (Taoism)|Three Treasures]] ({{zh|c=[[Wikt:三|三]][[Wikt:寶|寶]]|p=''sānbǎo''| w=''san-pao''}}), the basic [[virtues]] in [[Taoism]].
*The Three [[Dantian]]s
*The Three [[Dantian]]s
*Three Lines of a [[Ba Gua|Trigram]]
*Three Lines of a [[Bagua|Trigram]]
*[[Three Sovereigns]]: Heaven [[Fu Xi]] (Hand – Head – 3º Eye), Humanity [[Shen Nong]] ([[Liang Yi|Unit 69]]), Hell [[Nüwa]] (Foot – Abdomen – Umbiculus).
*[[Three Sovereigns]]: Heaven [[Fu Xi]] (Hand – Head – 3º Eye), Humanity [[Shen Nong]] ([[Liang Yi|Unit 69]]), Hell [[Nüwa]] (Foot – Abdomen – Umbiculus).


===Hinduism===
===Hinduism===
*The [[Trimurti]]: [[Brahma]] the Creator, [[Vishnu]] the Preserver, and [[Shiva]] the Destroyer.
*The [[Trimurti]]: [[Brahma]] the Creator, [[Vishnu]] the Preserver, and [[Shiva]] the Destroyer.
*The three [[Gunas]] found in [[Samkhya]] school of Hindu philosophy.<ref>James G. Lochtefeld, Guna, in The Illustrated Encyclopedia of Hinduism: A-M, Vol. 1, Rosen Publishing, {{ISBN|978-0-8239-3179-8}}, page 265</ref>
*The three [[guṇa]]s (''triguna'') found in the [[Samkhya]] school of Hindu philosophy.<ref>James G. Lochtefeld, Guna, in The Illustrated Encyclopedia of Hinduism: A-M, Vol. 1, Rosen Publishing, {{ISBN|978-0-8239-3179-8}}, page 265</ref>
*The three paths to salvation in the ''[[Bhagavad Gita]]'' named [[Karma Yoga]], [[Bhakti Yoga]] and [[Jnana Yoga]].
*The three paths to salvation in the ''[[Bhagavad Gita]]'' named [[Karma Yoga]], [[Bhakti Yoga]] and [[Jnana Yoga]].


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Three ({{lang|zh|三}}, formal writing: {{lang|zh|叁}}, [[pinyin]] ''sān'', [[Cantonese]]: ''saam''<sup>1</sup>) is considered a [[numerology|good number]] in [[Chinese culture]] because it sounds like the word "alive" ({{lang|zh|生}} pinyin ''shēng'', Cantonese: ''saang''<sup>1</sup>), compared to [[4 (number)|four]] ({{lang|zh|四}}, pinyin: ''sì'', Cantonese: ''sei''<sup>1</sup>), which sounds like the word "death" ({{lang|zh|死}} pinyin ''sǐ'', Cantonese: ''sei''<sup>2</sup>).
Three ({{lang|zh|三}}, formal writing: {{lang|zh|叁}}, [[pinyin]] ''sān'', [[Cantonese]]: ''saam''<sup>1</sup>) is considered a [[numerology|good number]] in [[Chinese culture]] because it sounds like the word "alive" ({{lang|zh|生}} pinyin ''shēng'', Cantonese: ''saang''<sup>1</sup>), compared to [[4 (number)|four]] ({{lang|zh|四}}, pinyin: ''sì'', Cantonese: ''sei''<sup>1</sup>), which sounds like the word "death" ({{lang|zh|死}} pinyin ''sǐ'', Cantonese: ''sei''<sup>2</sup>).


Counting to three is common in situations where a group of people wish to perform an action in [[Synchronization|synchrony]]: ''Now, on the count of three, everybody pull!'' Assuming the counter is proceeding at a uniform rate, the first two counts are necessary to establish the rate, and the count of "three" is predicted based on the timing of the "one" and "two" before it. Three is likely used instead of some other number because it requires the minimal amount counts while setting a rate. The number three is also closely associated with an extremely rare natural phenomenom called the triple, the triple was once caught by the eyes of two young men but is yet to be captured on film or relived, the knowledge of the triple is guarded by this pair until the end of time
Counting to three is common in situations where a group of people wish to perform an action in [[Synchronization|synchrony]]: ''Now, on the count of three, everybody pull!'' Assuming the counter is proceeding at a uniform rate, the first two counts are necessary to establish the rate, and the count of "three" is predicted based on the timing of the "one" and "two" before it. Three is likely used instead of some other number because it requires the minimal amount counts while setting a rate.

There is another superstition that it is unlucky to take a [[Three on a match (superstition)|third light]], that is, to be the third person to light a cigarette from the same match or lighter. This superstition is sometimes asserted to have originated among soldiers in the trenches of the First World War when a sniper might see the first light, take aim on the second and fire on the third.


There is another superstition that it is unlucky to take a [[Three on a match (superstition)|third light]], that is, to be the third person to light a cigarette from the same match or lighter. This superstition is sometimes asserted to have originated among soldiers in the trenches of the First World War when a sniper might see the first light, take aim on the second and fire on the third.{{citation needed|date=May 2021}}
The phrase "[[:wikt:Third time's the charm|Third time's the charm]]" refers to the superstition that after two failures in any endeavor, a third attempt is more likely to succeed. This is also sometimes seen in reverse, as in "third man [to do something, presumably forbidden] gets caught".


The phrase "[[:wikt:Third time's the charm|Third time's the charm]]" refers to the superstition that after two failures in any endeavor, a third attempt is more likely to succeed. This is also sometimes seen in reverse, as in "third man [to do something, presumably forbidden] gets caught". {{citation needed|date=May 2021}}
[[Luck]], especially bad luck, is often said to "come in threes".<ref>See "[http://www.encyclopedia.com/doc/1O214-bad.html bad]" in the ''Oxford Dictionary of Phrase and Fable'', 2006, via Encyclopedia.com.</ref>


[[Luck]], especially bad luck, is often said to "come in threes".<ref>See "[http://www.encyclopedia.com/doc/1O214-bad.html bad] {{Webarchive|url=https://web.archive.org/web/20090302124523/http://www.encyclopedia.com/doc/1O214-bad.html |date=2009-03-02 }}" in the ''Oxford Dictionary of Phrase and Fable'', 2006, via Encyclopedia.com.</ref>
==Sports==
* In [[American football|American]] and [[Canadian football]], a [[field goal]] is worth three points.
*In [[association football]]:
** For purposes of league standings, since the mid-1990s almost all leagues have awarded [[three points for a win]].
** A team that wins three trophies in a season is said to have won a [[Treble (association football)|treble]].
** A player who scores three goals in a match is said to have scored a [[hat-trick]].
* In [[baseball]]:
** A batter [[Strikeout|strikes out]] upon the third [[Strike zone|strike]] in any single batting appearance.
** Each team's half of an inning ends once the defense has recorded three outs (unless the home team has a [[Walk-off home run|walk-off hit]] in the ninth inning or any extra inning).
** In scorekeeping, "3" denotes the first baseman.
*In [[basketball]]:
** [[Three-point field goal|Three points]] are awarded for a basket made from behind a designated arc on the floor.
** The "3 position" is the [[small forward]].
*In [[bowling]], three [[strike (bowling)|strikes]] bowled consecutively is known as a "turkey".
* In [[cricket]], a bowler who is credited with dismissals of batsmen on three consecutive deliveries has achieved a "hat-trick".
*In [[Gaelic games]] (Gaelic football for [[Gaelic football|men]] and [[Ladies' Gaelic football|women]], [[hurling]], and [[camogie]]), three points are awarded for a goal, scored when the ball passes underneath the crossbar and between the goal posts.
*In [[ice hockey]]:
** Scoring three goals is called a "hat trick" (usually not hyphenated in North America).
** A team will typically have three [[Forward (ice hockey)|forwards]] on the ice at any given time.
* In [[professional wrestling]], a [[pin (professional wrestling)|pin]] is when one holds the opponent's shoulders against the mat for a count of three.
* In [[rugby union]]:
** A successful [[Penalty (rugby union)|penalty kick for goal]] or [[drop goal]] is worth three points.
** In the [[National Rugby League (France)|French variation]] of the [[Rugby union bonus points system|bonus points system]], a team receives a bonus point in the league standings if it wins a match while scoring at least three more tries than its opponent.
** The starting [[Rugby union positions|tighthead prop]] wears the jersey number 3.
* In [[rugby league]]:
** One of the two starting centres wears the jersey number 3. (An exception to this rule is the [[Super League]], which uses static squad numbering.)
*A "[[threepeat]]" is a term for winning three consecutive championships.
*A [[triathlon]] consists of three events: swimming, bicycling, and running.
*In many sports a competitor or team is said to win a [[Triple Crown (disambiguation)|Triple Crown]] if they win three particularly prestigious competitions.
* In [[volleyball]], once the ball is served, teams are allowed to touch the ball three times before being required to return the ball to the other side of the court, with the definition of "touch" being slightly different between indoor and beach volleyball.


==Film==
==Film==
{{for|a list of films called 3, Three, etc.|3 (disambiguation)#Film}}
{{for|a list of films called 3, Three, etc.|3 (disambiguation)#Film}}
*A number of film versions of the novel ''[[The Three Musketeers]]'' by [[Alexandre Dumas]]: ([[The Three Musketeers (1921 film)|1921]], [[The Three Musketeers (1933 serial)|1933]], [[The Three Musketeers (1948 film)|1948]], [[The Three Musketeers (1973 live-action film)|1973]], 1992, [[The Three Musketeers (1993 film)|1993]] & [[The Three Musketeers (2011 film)|2011]]).
*A number of film versions of the novel ''[[The Three Musketeers]]'' by [[Alexandre Dumas]]: ([[The Three Musketeers (1921 film)|1921]], [[The Three Musketeers (1933 serial)|1933]], [[The Three Musketeers (1948 film)|1948]], [[The Three Musketeers (1973 live-action film)|1973]], 1992, [[The Three Musketeers (1993 film)|1993]] and [[The Three Musketeers (2011 film)|2011]]).
*''[[3 Days of the Condor]]'' (1975), starring [[Robert Redford]], [[Faye Dunaway]], [[Cliff Robertson]], and [[Max von Sydow]].
*''[[3 Days of the Condor]]'' (1975), starring [[Robert Redford]], [[Faye Dunaway]], [[Cliff Robertson]], and [[Max von Sydow]].
*''[[Three Amigos]]'' (1986), comedy film starring [[Steve Martin]], [[Chevy Chase]], and [[Martin Short]].
*''[[Three Amigos]]'' (1986), comedy film starring [[Steve Martin]], [[Chevy Chase]], and [[Martin Short]].
Line 455: Line 463:
*''[[3 Days to Kill]]'' (2014), starring [[Kevin Costner]].
*''[[3 Days to Kill]]'' (2014), starring [[Kevin Costner]].
*''[[Three Billboards Outside Ebbing, Missouri]]'' (2017), starring [[Frances McDormand]], [[Woody Harrelson]], [[Sam Rockwell]].
*''[[Three Billboards Outside Ebbing, Missouri]]'' (2017), starring [[Frances McDormand]], [[Woody Harrelson]], [[Sam Rockwell]].
*The [[Minions (Despicable Me)|Minions]] from ''[[Despicable Me]]'' have [[Tridactyly|three digits]] on their hands.


==See also==
==See also==
{{Portal|Mathematics}}
{{Portal|Mathematics}}
*[[Cube (algebra)]] – (3 [[superscript]])
*[[Cube (algebra)]] – (3 [[superscript]])
*[[Thrice]]
*[[Third (disambiguation)|Third]]
*[[Third (disambiguation)|Third]]
*[[Triad (disambiguation)|Triad]]
*[[Triad (disambiguation)|Triad]]
*[[Trio (disambiguation)|Trio]]
*[[Rule of three (disambiguation)|Rule of three]]
*[[List of highways numbered 3]]
*[[List of highways numbered 3]]


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{{Commons category}}
{{Commons category}}
*[https://web.archive.org/web/20071023064015/http://threes.com/ Tricyclopedic Book of Threes] by Michael Eck
*[https://web.archive.org/web/20071023064015/http://threes.com/ Tricyclopedic Book of Threes] by Michael Eck
*[http://www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/Threes.html Threes in Human Anatomy] by Dr. John A. McNulty
*[http://www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/Threes.html Threes in Human Anatomy] by John A. McNulty
*{{cite web|last=Grime|first=James|title=3 is everywhere|url=http://www.numberphile.com/videos/three.html|work=Numberphile|publisher=[[Brady Haran]]|access-date=2013-04-13|archive-url=https://web.archive.org/web/20130514230849/http://www.numberphile.com/videos/three.html|archive-date=2013-05-14|url-status=dead}}
*{{cite web|last=Grime|first=James|title=3 is everywhere|url=http://www.numberphile.com/videos/three.html|work=Numberphile|publisher=[[Brady Haran]]|access-date=2013-04-13|archive-url=https://web.archive.org/web/20130514230849/http://www.numberphile.com/videos/three.html|archive-date=2013-05-14|url-status=dead}}
*[https://web.archive.org/web/20140201161634/http://numdic.com/3 The Number 3]
*[https://web.archive.org/web/20140201161634/http://numdic.com/3 The Number 3]

Latest revision as of 11:39, 19 May 2024

← 2 3 4 →
−1 0 1 2 3 4 5 6 7 8 9
Cardinalthree
Ordinal3rd
(third)
Numeral systemternary
Factorizationprime
Prime2nd
Divisors1, 3
Greek numeralΓ´
Roman numeralIII, iii
Greek prefixtri-
Latin prefixtre-/ter-
Binary112
Ternary103
Senary36
Octal38
Duodecimal312
Hexadecimal316
Arabic, Kurdish, Persian, Sindhi, Urdu٣
Bengali, Assamese
Chinese三,弎,叄
Devanāgarī
Ge'ez
Greekγ (or Γ)
Hebrewג
Japanese三/参
Khmer
ArmenianԳ
Malayalam
Tamil
Telugu
Kannada
Thai
N'Ko߃
Lao
GeorgianႢ/ⴂ/გ (Gani)
Babylonian numeral𒐗
Maya numerals•••
Morse code... _ _

3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious and cultural significance in many societies.

Evolution of the Arabic digit[edit]

The use of three lines to denote the number 3 occurred in many writing systems, including some (like Roman and Chinese numerals) that are still in use. That was also the original representation of 3 in the Brahmic (Indian) numerical notation, its earliest forms aligned vertically.[1] However, during the Gupta Empire the sign was modified by the addition of a curve on each line. The Nāgarī script rotated the lines clockwise, so they appeared horizontally, and ended each line with a short downward stroke on the right. In cursive script, the three strokes were eventually connected to form a glyph resembling a ⟨3⟩ with an additional stroke at the bottom: .

The Indian digits spread to the Caliphate in the 9th century. The bottom stroke was dropped around the 10th century in the western parts of the Caliphate, such as the Maghreb and Al-Andalus, when a distinct variant ("Western Arabic") of the digit symbols developed, including modern Western 3. In contrast, the Eastern Arabs retained and enlarged that stroke, rotating the digit once more to yield the modern ("Eastern") Arabic digit "٣".[2]

In most modern Western typefaces, the digit 3, like the other decimal digits, has the height of a capital letter, and sits on the baseline. In typefaces with text figures, on the other hand, the glyph usually has the height of a lowercase letter "x" and a descender: "". In some French text-figure typefaces, though, it has an ascender instead of a descender.

A common graphic variant of the digit three has a flat top, similar to the letter Ʒ (ezh). This form is sometimes used to prevent falsifying a 3 as an 8. It is found on UPC-A barcodes and standard 52-card decks.

Mathematics[edit]

According to Pythagoras and the Pythagorean school, the number 3, which they called triad, is the only number to equal the sum of all the terms below it, and the only number whose sum with those below equals the product of them and itself.[3]

Divisibility rule[edit]

A natural number is divisible by three if the sum of its digits in base 10 is divisible by 3. For example, the number 21 is divisible by three (3 times 7) and the sum of its digits is 2 + 1 = 3. Because of this, the reverse of any number that is divisible by three (or indeed, any permutation of its digits) is also divisible by three. For instance, 1368 and its reverse 8631 are both divisible by three (and so are 1386, 3168, 3186, 3618, etc.). See also Divisibility rule. This works in base 10 and in any positional numeral system whose base divided by three leaves a remainder of one (bases 4, 7, 10, etc.).

Properties of the number[edit]

3 is the second smallest prime number and the first odd prime number. It is the first unique prime, such that the period length value of 1 of the decimal expansion of its reciprocal, 0.333..., is unique. 3 is a twin prime with 5, and a cousin prime with 7, and the only known number such that ! − 1 and ! + 1 are prime, as well as the only prime number such that − 1 yields another prime number, 2. A triangle is made of three sides. It is the smallest non-self-intersecting polygon and the only polygon not to have proper diagonals. When doing quick estimates, 3 is a rough approximation of π, 3.1415..., and a very rough approximation of e, 2.71828...

3 is the first Mersenne prime, as well as the second Mersenne prime exponent and the second double Mersenne prime exponent, for 7 and 127, respectively. 3 is also the first of five known Fermat primes, which include 5, 17, 257, and 65537. It is the second Fibonacci prime (and the second Lucas prime), the second Sophie Germain prime, the third Harshad number in base 10, and the second factorial prime, as it is equal to 2! + 1.

3 is the second and only prime triangular number, and Gauss proved that every integer is the sum of at most 3 triangular numbers.

Three is the only prime which is one less than a perfect square. Any other number which is − 1 for some integer is not prime, since it is ( − 1)( + 1). This is true for 3 as well (with = 2), but in this case the smaller factor is 1. If is greater than 2, both − 1 and + 1 are greater than 1 so their product is not prime.

Related properties[edit]

The trisection of the angle was one of the three famous problems of antiquity.

3 is the number of non-collinear points needed to determine a plane, a circle, and a parabola.

There are only three distinct 4×4 panmagic squares.

Three of the five Platonic solids have triangular faces – the tetrahedron, the octahedron, and the icosahedron. Also, three of the five Platonic solids have vertices where three faces meet – the tetrahedron, the hexahedron (cube), and the dodecahedron. Furthermore, only three different types of polygons comprise the faces of the five Platonic solids – the triangle, the square, and the pentagon.

There are three finite convex uniform polytope groups in three dimensions, aside from the infinite families of prisms and antiprisms: the tetrahedral group, the octahedral group, and the icosahedral group. In dimensions ⩾ 5, there are only three regular polytopes: the -simplexes, -cubes, and -orthoplexes. In dimensions 9, the only three uniform polytope families, aside from the numerous infinite proprismatic families, are the simplex, cubic, and demihypercubic families. For paracompact hyperbolic honeycombs, there are three groups in dimensions 6 and 9, or equivalently of ranks 7 and 10, with no other forms in higher dimensions. Of the final three groups, the largest and most important is , that is associated with an important Kac–Moody Lie algebra .[4]

Numeral systems[edit]

There is some evidence to suggest that early man may have used counting systems which consisted of "One, Two, Three" and thereafter "Many" to describe counting limits. Early peoples had a word to describe the quantities of one, two, and three but any quantity beyond was simply denoted as "Many". This is most likely based on the prevalence of this phenomenon among people in such disparate regions as the deep Amazon and Borneo jungles, where western civilization's explorers have historical records of their first encounters with these indigenous people.[5]

List of basic calculations[edit]

Multiplication 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 50 100 1000 10000
3 × x 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 150 300 3000 30000
Division 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
3 ÷ x 3 1.5 1 0.75 0.6 0.5 0.428571 0.375 0.3 0.3 0.27 0.25 0.230769 0.2142857 0.2 0.1875 0.17647058823529411 0.16 0.157894736842105263 0.15
x ÷ 3 0.3 0.6 1 1.3 1.6 2 2.3 2.6 3 3.3 3.6 4 4.3 4.6 5 5.3 5.6 6 6.3 6.6
Exponentiation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
3x 3 9 27 81 243 729 2187 6561 19683 59049 177147 531441 1594323 4782969 14348907 43046721 129140163 387420489 1162261467 3486784401
x3 1 8 27 64 125 216 343 512 729 1000 1331 1728 2197 2744 3375 4096 4913 5832 6859 8000

Science[edit]

Engineering[edit]

  • The triangle, a polygon with three edges and three vertices, is the most stable physical shape. For this reason it is widely utilized in construction, engineering and design.[9]

Protoscience[edit]

Pseudoscience[edit]

Philosophy[edit]

Religion[edit]

Symbol of the Triple Goddess showing the waxing, full and waning Moon

Many world religions contain triple deities or concepts of trinity, including the Hindu Trimurti and Tridevi, the Triglav (lit. "Three-headed one"), the chief god of the slavs, the three Jewels of Buddhism, the three Pure Ones of Taoism, the Christian Holy Trinity, and the Triple Goddess of Wicca.

The Shield of the Trinity is a diagram of the Christian doctrine of the Trinity.

Christianity[edit]

Judaism[edit]

Islam[edit]

  • The three core principles in Shia tradition: Tawhid (Oneness of God), Nabuwwa (Concept of Prophethood), Imama (Concept of Imam)

Buddhism[edit]

  • The Triple Bodhi (ways to understand the end of birth) are Budhu, Pasebudhu, and Mahaarahath.
  • The Three Jewels, the three things that Buddhists take refuge in.

Shinto[edit]

Daoism[edit]

Hinduism[edit]

Zoroastrianism[edit]

  • The three virtues of Humata, Hukhta and Huvarshta (Good Thoughts, Good Words and Good Deeds) are a basic tenet in Zoroastrianism.

Norse mythology[edit]

Three is a very significant number in Norse mythology, along with its powers 9 and 27.

  • Prior to Ragnarök, there will be three hard winters without an intervening summer, the Fimbulwinter.
  • Odin endured three hardships upon the World Tree in his quest for the runes: he hanged himself, wounded himself with a spear, and suffered from hunger and thirst.
  • Bor had three sons, Odin, Vili, and .

Other religions[edit]

Esoteric tradition[edit]

As a lucky or unlucky number[edit]

Three (, formal writing: , pinyin sān, Cantonese: saam1) is considered a good number in Chinese culture because it sounds like the word "alive" ( pinyin shēng, Cantonese: saang1), compared to four (, pinyin: , Cantonese: sei1), which sounds like the word "death" ( pinyin , Cantonese: sei2).

Counting to three is common in situations where a group of people wish to perform an action in synchrony: Now, on the count of three, everybody pull! Assuming the counter is proceeding at a uniform rate, the first two counts are necessary to establish the rate, and the count of "three" is predicted based on the timing of the "one" and "two" before it. Three is likely used instead of some other number because it requires the minimal amount counts while setting a rate.

There is another superstition that it is unlucky to take a third light, that is, to be the third person to light a cigarette from the same match or lighter. This superstition is sometimes asserted to have originated among soldiers in the trenches of the First World War when a sniper might see the first light, take aim on the second and fire on the third.[citation needed]

The phrase "Third time's the charm" refers to the superstition that after two failures in any endeavor, a third attempt is more likely to succeed. This is also sometimes seen in reverse, as in "third man [to do something, presumably forbidden] gets caught". [citation needed]

Luck, especially bad luck, is often said to "come in threes".[23]

Film[edit]

See also[edit]

References[edit]

  1. ^ Smith, David Eugene; Karpinski, Louis Charles (1911). The Hindu-Arabic numerals. Boston; London: Ginn and Company. pp. 27–29, 40–41.
  2. ^ Georges Ifrah, The Universal History of Numbers: From Prehistory to the Invention of the Computer transl. David Bellos et al. London: The Harvill Press (1998): 393, Fig. 24.63
  3. ^ Priya Hemenway (2005), Divine Proportion: Phi In Art, Nature, and Science, Sterling Publishing Company Inc., pp. 53–54, ISBN 1-4027-3522-7
  4. ^ Allcock, Daniel (May 2018). "Prenilpotent Pairs in the E10 root lattice" (PDF). Mathematical Proceedings of the Cambridge Philosophical Society. 164 (3): 473–483. Bibcode:2018MPCPS.164..473A. doi:10.1017/S0305004117000287. S2CID 8547735. Archived (PDF) from the original on 2022-11-03. Retrieved 2022-11-03.
    "The details of the previous section were E10-specific, but the same philosophy looks likely to apply to the other symmetrizable hyperbolic root systems...it seems valuable to give an outline of how the calculations would go", regarding E10 as a model example of symmetrizability of other root hyperbolic En systems.
  5. ^ Gribbin, Mary; Gribbin, John R.; Edney, Ralph; Halliday, Nicholas (2003). Big numbers. Cambridge: Wizard. ISBN 1840464313.
  6. ^ Harari, H. (1977). "Three generations of quarks and leptons" (PDF). In van Goeler, E.; Weinstein, R. (eds.). Proceedings of the XII Rencontre de Moriond. p. 170. SLAC-PUB-1974.
  7. ^ Adair, R.K. (1989). The Great Design: Particles, Fields, and Creation. Oxford University Press. p. 214. Bibcode:1988gdpf.book.....A.
  8. ^ Barrow-Green, June (2008). "The Three-Body Problem". In Gowers, Timothy; Barrow-Green, June; Leader, Imre (eds.). The Princeton Companion to Mathematics. Princeton University Press. pp. 726–728.
  9. ^ "Most stable shape- triangle". Maths in the city. Retrieved February 23, 2015.
  10. ^ Eric John Holmyard. Alchemy. 1995. p.153
  11. ^ Walter J. Friedlander. The golden wand of medicine: a history of the caduceus symbol in medicine. 1992. p.76-77
  12. ^ Churchward, James (1931). "The Lost Continent of Mu – Symbols, Vignettes, Tableaux and Diagrams". Biblioteca Pleyades. Archived from the original on 2015-07-18. Retrieved 2016-03-15.
  13. ^ "Encyclopaedia Britannica". Lexikon des Gesamten Buchwesens Online (in German). doi:10.1163/9789004337862_lgbo_com_050367.
  14. ^ T. E. T. (25 January 1877). "The Encyclopaedia Britannica". Nature. XV (378): 269–271. Archived from the original on 24 July 2020. Retrieved 12 July 2019.
  15. ^ Marcus, Rabbi Yossi (2015). "Why are many things in Judaism done three times?". Ask Moses. Archived from the original on 2 April 2015. Retrieved 16 March 2015.
  16. ^ "Shabbat". Judaism 101. 2011. Archived from the original on 29 June 2009. Retrieved 16 March 2015.
  17. ^ Kitov, Eliyahu (2015). "The Three Matzot". Chabad.org. Archived from the original on 24 March 2015. Retrieved 16 March 2015.
  18. ^ Kaplan, Rabbi Aryeh (28 August 2004). "Judaism and Martyrdom". Aish.com. Archived from the original on 20 March 2015. Retrieved 16 March 2015.
  19. ^ "The Basics of the Upsherin: A Boy's First Haircut". Chabad.org. 2015. Archived from the original on 22 March 2015. Retrieved 16 March 2015.
  20. ^ "The Conversion Process". Center for Conversion to Judaism. Archived from the original on 23 February 2021. Retrieved 16 March 2015.
  21. ^ Kaplan, Aryeh. "The Soul Archived 2015-02-24 at the Wayback Machine". Aish. From The Handbook of Jewish Thought (Vol. 2, Maznaim Publishing. Reprinted with permission.) September 4, 2004. Retrieved February 24, 2015.
  22. ^ James G. Lochtefeld, Guna, in The Illustrated Encyclopedia of Hinduism: A-M, Vol. 1, Rosen Publishing, ISBN 978-0-8239-3179-8, page 265
  23. ^ See "bad Archived 2009-03-02 at the Wayback Machine" in the Oxford Dictionary of Phrase and Fable, 2006, via Encyclopedia.com.

External links[edit]