# Symbol

a symbol is a symbol for the name of an object for use in formulas.

In principle any symbol can be used as symbols. It is written in place of the object name and is identical to its meaning. That means that a symbol always by thatit assigned object names to be replaced knows and in reverse.

Symbols are used particularly in mathematics and in nature and engineering sciences.

## standards

Numerous symbols are standardized (z. B. internationally [itex] =< /math> for „“or math V [/itex] is <alike> for the volume). Such standardizations are for example ISO 31 and DIN 1304.

If as symbols letters are used, are used particularly frequently the German (latin), Greek, old-German and Hebrew alphabet.Most letter symbols consist only few of and of more than one letter. In order to extend the character set, the letters indices from letters or numbers are often attached.

## mathematical symbols

### variable objects

in mathematics become in thatRule letter as symbols uses, if it concerns variable objects. For the text record a serif writing is usually used.

Examples for rule of the used alphabet and the text record:

• Scalar one: [itex] a=7< /math>
• Vectors: fat or with overarrow. [itex] \ vec F \ equiv \ mathbf {F} =m \ cdot \ mathbf {A}< /math>. In former times also small lettersin german type writing: [itex] \ mathfrak {x} = \ left (0 \ 2 \ 1 \ right) ^T< /math>
• Quantities: largely; fat or with double senkrechten lines [itex] 3 \ in \ mathbf {N} \ equiv \ mathbb {N}< /math>
• Stencils: serifless [itex] \ December (\ mathsf {M}) =4< /math>. In former times also: Capital letter in german type writing< math> \ mathfrak {E}: = \ begin {pmatrix} 1 & \ cdots & 0 \ \ \ vdots & \ ddots & \ vdots\ \ 0 & \ cdots & 1 \ end {pmatrix} <to /math>

### remaining objects

other objects, e.g. Instructions contained, get special symbols assigned, which originate only partially (originally) from alphabets.

Examples:

• [itex]: =< /math> Assignment operator: [itex] A: =3< /math>
• [itex]<< /math> Comparison „smaller than “: [itex] A< 7< /math>
• [itex]>< /math> Comparison „more largelyas “: [itex] 7> A< /math>
• + add operator: [itex] a+4=7< /math>
• [itex] \ sum< /math> Sum: [itex] a= \ sum_ {i=1} ^ {n} a_ {i}< /math>
• () Changing the analysis sequence: [itex] 3a+7 \ neq 3 (a+7)< /math>
• Constant one: [itex] \ pi \ approx 3 {,} 14159< /math>

## physical symbols

the symbols used in physics consist of latin or a Greek letter. Their sentence takes place (according to DIN 1313) italically with serifs.

Sample applications: