Arrow (symbol)

Arrow on a sign

An arrow is a symbol consisting of a line and a tip attached to the line.

The most common function is the route display. However, there are many different arrow symbols that are used in other contexts:

The use of symbolic arrows to indicate direction can be proven since the 18th century. The illustration of a pointing hand (manicle, Latin for "small hand") or even a foot is much older.

mathematics

In mathematics arrows have different meanings:

${\ displaystyle \! \ a_ {n} \ rightarrow b}$ means: "(The consequence ) converges against (for )" ${\ displaystyle \! \ a_ {n}}$ ${\ displaystyle \! \ b}$ ${\ displaystyle \! \ n \ rightarrow \ infty}$
${\ displaystyle \! \ a \ Rightarrow b}$ means: " follows from " ${\ displaystyle \! \ a}$ ${\ displaystyle \! \ b}$
${\ displaystyle a \ Leftrightarrow b}$ means: " is equivalent to " or "exactly if" ${\ displaystyle \! \ a}$ ${\ displaystyle \! \ b}$
${\ displaystyle f \ !: x \ mapsto x ^ {2} -5}$ defines a function with the property: ${\ displaystyle f (x) = x ^ {2} -5}$
${\ displaystyle f \ !: A \ rightarrow B}$ denotes a function having a definition set and a target set ; Special forms such as or for injective or surjective functions are also common. ${\ displaystyle f}$ ${\ displaystyle A}$ ${\ displaystyle B}$ ${\ displaystyle A \ hookrightarrow B}$ ${\ displaystyle A \ twoheadrightarrow B}$

An arrow above a symbol ( ) means that it is a vector . ${\ displaystyle {\ vec {x}}}$

Some of these arrows have other meanings in specialty areas of mathematics. For example, “ ” is used in logic to express an object-language implication . ${\ displaystyle \ rightarrow}$

Arrow symbols in chemistry using the example of the reactions of molecular bromine, Br ₂ . Reaction arrows are marked blue in the figure above and below .
Above: Homolytic cleavage of a bond through the displacement of two individual electrons with the formation of two radicals. The curved arrows are marked in red and have only one hook at the tip of the arrow , since only one electron is shifted. -
Below: Heterolytic cleavage of a bond with the formation of a cation (lower left) and an anion (lower right). The curved arrow is marked in red and has two hooks at the tip of the arrow , as two electrons are moved.
Note: The coloring is for illustration only.

chemistry

In the chemical be in reaction equations in the synthesis planning, description, mesomeric forms or for shifting of electrons in reaction mechanisms arrows in different shapes used .

They are also used in chemistry and physics to represent individual electrons (↑) and electron pairs (⇅ or ⇈) in molecular orbital diagrams or to represent the electron spin , as well as the nuclear spin .

traffic

Arrows have different meanings in road traffic: an arrow on a lane either indicates (or announces) a lane to turn, or indicates the imminent end of the lane and prompts the driver to change to another lane. On several traffic signs (eg: "Priority over oncoming traffic ", "Oncoming traffic has priority", "(Restricted) stopping prohibition beginning / further / end") arrows describe traffic flows or indicate the scope of the traffic sign. In addition, signs are often in the shape of an arrow to indicate their direction.

Enumerations

In enumerations of the arrow is often called Bullet ( enumeration symbol used) instead of an indent.

Schematic drawings and plans

Arrow made of stones as a signpost

Recycling symbol

As of placement on maps or as an indicator of a particular position he has been a north arrow widespread and shows on cards as a simplified compass rose to the north .

typography

In typography , a plurality of arrows is used, including, for example: ➢, ➔, ➡, ➸, →. The left arrow (←) is rarely used, except on the computer keyboard, where it labels the Backspace key.

The index finger ☞ was a substitute for an arrow in texts until the 20th century.

Lexicons

In a lexicon entry , an arrow in front of another word refers to an article with the same name. Depending on the typography of the lexicon, the arrow symbol points to the right (→) or up (↑).

The arrow can either serve as a forwarding in the sense of "see below" ( Zuckergast → Silberfischchen ) or a reference to a further article ( Willberg, Hans Peter (* October 4, 1930 in Nuremberg, † May 29, 2003) was a German → Typographer ).

The arrow is mainly used in printed dictionaries because it can be replaced by a hyperlink in digital reference works .

computer

In the computer character code Unicode there is a separate code block for arrow symbols, the Unicode block arrows ( Arrows ), the area code to 2190 ₁₆ to 21FF ₁₆ is, and incorporates many of the symbols described above.

The original ASCII from 1963 contained the arrows ← and ↑. ISO 6937 contains the arrows ←, ↑, → and ↓.

Dentistry

In the diagnostic scheme in dentistry , tilted or elongated (seemingly elongated) teeth are characterized with arrows that indicate the direction of the tilt, elongation or tooth migration : → or ←, ↑ or ↓. A gap closure after a tooth loss is indicated by two opposite brackets) (. If the gap has been closed by tooth migration, additional arrows are indicated before and after the brackets: →) (←.

keyboard

On InduS keyboards and in modern Linux distributions, the keys Alt Gr+ z; u; iassigned with ←; ↓; →; Alt Gr+ Shift+ uwith ↑.

Individual evidence

^ Robert J. Finkel: History of the Arrow . 2015
↑ http://www.manikel.de
↑ Quantities, Units and Symbols in Physical Chemistry (“Green Book”; PDF; 2.0 MB), IUPAC .
^ Rudolf W. Ott: Clinic and Practice Guide Dentistry . Georg Thieme Verlag, 2003, ISBN 978-3-13-131781-0 , p. 448.

Web links

Commons : arrow symbols - collection of images

[1] Robert J. Finkel: History of the Arrow . 2015

[2] ttp://www.manikel.de

[3] Quantities, Units and Symbols in Physical Chemistry (“Green Book”; PDF; 2.0 MB), IUPAC .

[4] Rudolf W. Ott: Clinic and Practice Guide Dentistry . Georg Thieme Verlag, 2003, ISBN 978-3-13-131781-0 , p. 448.