Four

This article is about the number four . For the year 4 AD, see 4 , for additional meanings see Four (disambiguation) .

Four
4th
presentation
Roman	IV
dual	100
Octal	4th
Duodecimal	4th
Hexadecimal	4th
Morse code	· · · · -
Arabic	٤
Chinese	四
Mathematical properties
sign	positive
parity	straight
Factorization	${\displaystyle 2^{2}}$
Divider	1, 2, 4

Seven segment representation of the four

A continental European handwritten four and a notation common in the English-speaking world

Four in flag alphabet

Half eight as four in round spelling in the year 1497

Half eight as four in square spelling in the year 1488

The four (4) is the natural number between three and five . It's even and a square number .

mathematics

The four is straight. It is the first composite number and thus the first non- prime number after the one .

The peculiarity of the four is that both and and thus apply. This can even be generalized using the arrow notation. It applies to any natural : ${\displaystyle 2+2=4}$ ${\displaystyle 2\cdot 2=4}$ ${\displaystyle 2^{2}=4}$ ${\displaystyle n}$

${\displaystyle 4=2\ \underbrace {\uparrow \ \uparrow \cdots \uparrow } _{n\ \mathrm {mal} }\ 2}$.

The operator in the famous Pythagorean triple can be "scooped" from the (degenerate) triple using the four operators required to calculate all primitive Pythagorean triples . ${\displaystyle 4}$ ${\displaystyle (3,4,5)}$ ${\displaystyle 0}$ ${\displaystyle (1,0,1)}$

Four points span a square , a surface with four sides, in the plane . It is the simplest figure that can be deformed while retaining its side lengths, for example from a rectangle to a parallelogram.

A maximum of four points can be equidistant in space, i.e. H. at the same distance from each other. These then form a tetrahedron , a body with four equal triangular sides.

The four-color theorem states that four colors are sufficient to color all areas on a map in such a way that areas of the same color (along borders) do not collide anywhere, whereas three colors are not sufficient for this.

Another peculiarity of the four is the impossibility of solving an algebraic equation of a higher degree than four with the help of extracting the roots and simple arithmetic operations. The mathematician Niels Henrik Abel published his proof of this in 1826 .

Four is a Størmer number .

Spellings

The number has different glyphs depending on the age and language :

The spelling in the Roman numerals is IV, the Arabic ٤. In Urdu (India, Pakistan) it is ۴, in Devanagari (India) it is ४ and in Hebrew it is ד. In the European Middle Ages , the spelling was common as half an eight.

In Germany, the number 4 is handwritten in two lines according to the numerical spelling of the Latin original script : a right angle with a longer vertical line. This notation corresponds to the Austrian school script (both versions from 1969 and 1995) and the Swiss Schnürlischrift . In the English-speaking culture and in areas influenced by it, a 4 is drawn mostly closed.

The four is often represented as IIII on the dials of clocks with Roman writing.

Linguistic

The Latin word for four is quattuor , the associated ordinal number quartus (the fourth) and the adjective quadrus (square) found their way into German with terms such as quarter , fourth , quartile , quartet or square .

The Greek prefix for four τετρα- (tetra-) was used for foreign words such as tetralogy , tetrarchy , tetrahedron or tetrachord .

Natural sciences

biology

The information of the genome of all earthly life stored in the deoxyribonucleic acid is encoded in triplet sequences, which consist of four different basic units: the nucleobases adenine (A), thymine (T), guanine (G) and cytosine (C).

The land vertebrates (tetrapods) , the quadruped land vertebrates, basically each have four extremities, the elementary importance of which is locomotion. Individual tetrapods can have all or some of the extremities regressed or remodeled, such as snakes that no longer have locomotion-capable extremities or humans in whom the front extremities are no longer suitable for locomotion. The tetrapods include amphibians (amphibians), reptiles (reptiles), mammals and birds.

chemistry

The number 4 is the ordinal number of the alkaline earth metal beryllium in the periodic table .

The carbon atom has the property of four covalent bonds to establish in tetrahedral angles and thereby can the extremely hard diamond and a wide variety of organic molecules of chains with ramifications, chirality , double bonds, to form to ring systems.

medicine

Quads

In orthopedics , the four-digit symbol is a clinical test to test the functionality of the hip joint in humans. When lying down, one leg is bent to a four across the body axis.

Culture, literature, music, society and intellectual life

The Greek natural philosophers saw four elements (fire, water, earth, air) as the basic components of all being: the four-element doctrine is still effective today. Since there are four cardinal points, seasons and temperaments in addition to the four elements , the four was considered the number of the earthly in the Middle Ages, in contrast to the three , the number of God and the Trinity . From the arithmetical connections of these numbers three and four there are other numbers that are sacred in Christianity: seven and twelve . From this Christian doctrine of numbers, the conception arises for music that the 3/4 time is considered perfect - previously represented by a circle, while the 4/4 time is considered the imperfect, earthly one, which is still in the today musical notation is indicated by a semicircle, a character similar to the capital C.

In the number symbolism it stands for the cross, among other things. It crosses in its representation and the cross has four corners. It therefore stands for death and suffering in general. In the Chinese number symbolism and also in Korea and Japan, the four is considered an unlucky number , as its sound ( Chinese  四 , Pinyin sì ) is similar to the Chinese word for death ( Chinese  死 , Pinyin sǐ ) see: tetraphobia .

Sports

The number 4 on the back is the number of the pre-stopper / central defender in football.

More terms with the four

• Four Treasures of the Scholars' Room (Items a Chinese Scholar Needed to Write and Paint on)
• Four Seasons
• Gang of Four (group of left-wing leaders of the Chinese Communist Party, which wielded great power before Mao Zedong's death)
• Foursome (rowing boat with or without a helmsman)
• Transept (name of the space that is created when the main and transepts of a church meet)
• Quaternary (objects made up of four parts)
• Connect four , strategy game
• Four paws , animal welfare organization
• Four-species machine , mechanical adding machine

mathematics

• Four color set
• Four squares set
• Four fours , a math puzzle
• The four basic arithmetic operations

communication

• Four-eyes principle
• Four-sided model

Sports

• Four continents championships , figure skating competition
• The four musketeers , tennis team
• Four Hills Tournament , ski jumping competition
• Four days of Dunkirk , bike races
• Back four , a formation in football

history

• The Four Freedoms , by US President Roosevelt
• Four old men , the battle slogan of the Chinese Cultural Revolution
• Four basic principles , political doctrine by Deng Xiaoping
• Four modernizations , Chinese economic program
• Four beauties , figures in Chinese history

media

• Four against Willi , TV show, ARD
• Here from four , live magazine MDR
• Bremen Four , Radio Bremen
• Factor four , environmental report

religion

Christianity

• The four horsemen of the apocalyptic , biblical motif
• The four evangelists , writers of the gospels in the New Testament
• The four archangels
• The four cardinal virtues in ethics
• The four last things in eschatology
• Four Marshals of God , saints of early Christianity
• Four main church modes (Protus, Deuterus, Tritus and Tetrardus)
• The four Sundays of Advent

Further

• Four Noble Truths , Buddhism
• The four immeasurable , in Buddhism
• Four books , canonical books of Confucianism
• Four valleys , Sufi-mystical work by Baha'u'llah

Geographic

• Vier- und Marshland
• Administrative community Vier Berge-Teucherner Land

Literary title

• The mark of four , Arthur Conan Doyle
• Four classic novels , in Chinese literature
• The big four , Agatha Christie
• The four artful brothers , fairy tales by the Brothers Grimm
• The four (comic)

Movie title

• The Last Four , American drama directed by George Archainbaud
• Four fists against Rio , Italian comedy film by EB Clucher (pseudonym of Enzo Barboni)
• Four fists for a hallelujah , Italian western parody by Enzo Barboni
• Four women in the house , German television series by Hans-Georg Thiemt and Hans-Dieter Schreeb, director: Hermann Leitner
• Four women and a death , Austrian crime series based on an idea by Wolf Haas
• Four Love You , American comedy film by Harold Ramis
• Four in a red circle , French crime film by Jean-Pierre Melville
• Four Weird Birds , American crime comedy directed by Peter Yates
• The dreaded four , American late wests by Richard Brooks
• Die Vier im Jeep , Swiss film drama by Leopold Lindtberg
• Four Brothers , American action film directed by John Singleton
• Four minutes , German drama by Chris Kraus
• Four Sisters , American drama directed by George Cukor
• I'm number four , American action thriller from DJ Caruso
• One for 4 , American comedy film directed by Ken Kwapis
• Vier gegen die Bank (1976) , German crime comedy by Wolfgang Petersen
• Vier gegen die Bank (2016) , German comedy film by Wolfgang Petersen
• The four feathers , different productions

art

• The Blue Four Exhibition Association
• The four apostles , painting
• The four fountains , fountain system in Rome
• Vier Weltweise , motif on church clocks
• Four elements (Arcimboldo)
• Four times of the day , group of statues

music

• For four hands , playing instructions for piano
• Four last songs , Richard Strauss
• Vierklang
• Die Fantastischen Vier , German hip-hop band

additional

• Four great inventions of ancient China
• Four Sephardic Synagogues (Jerusalem) , Jerusalem
• Four for an Ave Maria , spaghetti western
• Four arts
• Four nations tournament , for women's soccer teams
• Four kingdoms doctrine , Bible
• Four-stroke engine
• Four-wave mix
• The last four things
• Four tier system
• Council of Four , decision-makers after the First World War
• Four-vector , concept of the theory of relativity
• Four phases of the moon
• The big four (German EVU)
• The Big Four (Japan)

See also

• Big Four (banks)
• Big Four (accounting firms)
• Big Four (snakes)
• The Big Four Live from Sofia, Bulgaria

literature

• Paul von Naredi-Rainer: The number four in architecture and urban planning . In: INSITU. Zeitschrift für Architekturgeschichte 4 (2/2012), pp. 149–160.

Web links

Commons : Four  - collection of pictures, videos and audio files

Wiktionary: Four  - explanations of meanings, word origins, synonyms, translations

Individual evidence

1. ^ Georges Ifrah, David Bellos, EF Harding, Sophie Wood and Ian Monk: The Universal History of Numbers: From Prehistory to the Invention of the Computer. London (Wiley & Sons), 1999. ISBN 9780471375685 .