# Unit symbol

The unit symbol , even unit abbreviation is an abbreviation for a unit of the indication of a physical quantity to which even the numerical value, called the measure is needed. In a system of units , the assignment of units of measurement to the physical phenomena is defined. In most countries the unit symbols of the SI system of units are defined according to EN ISO 80000-1 , in Germany also according to DIN 1301 . In addition, many countries have legislation on units of measurement, related spellings and symbols.

## example

An example of the use of a unit symbol for the physical quantity is the electrical voltage :

The unit of measurement is volts with the symbol V:

Voltage U = { U } [ U ] = 20 V

With

{ U } = 20 (read: the measure of voltage is 20)
[ U ] = V (read: the unit of measurement for voltage is the volt)

## Unit symbols in typesetting

A unit symbol is written vertically (straight) in accordance with DIN 1301-1 and DIN 1338, regardless of the font used in the rest of the text. It follows the numerical value after a distance. A narrow or a normal non-breaking space is recommended in the typesetting . Exceptions only apply to the (stand-alone) characters °, ′, ″ ( degrees ) that immediately follow the numerical value. For unit symbols that contain a degree symbol, such as degrees Celsius (° C), a space is also set.

Hints:

• Placing the unit symbol in square brackets, as it can be found in some texts (e.g. for labeling the axes of diagrams ), contradicts the standards DIN 461 , DIN 1313 and EN ISO 80000-1.
• No indices should be attached to unit symbols; however, the basic symbols can be added to formula symbols (symbols for physical quantities) (DIN 1304 and DIN 1338). For example, the notation should be used for a voltage with an effective value of 20 volts ; the notation would only be appropriate if there were several definitions of the volt to distinguish.${\ displaystyle U}$${\ displaystyle U _ {\ mathrm {eff}} = 20 \, \ mathrm {V}}$${\ displaystyle U = 20 \, \ mathrm {V_ {eff}}}$