Abbreviation - Measurement Shorthand – Symbol or Abbreviation

Measurement Shorthand – Symbol or Abbreviation

Writers often use shorthand to denote units of measure. Such shorthand can be an abbreviation, such as "in" for "inch" or can be a symbol such as "km" for "kilometre".

The shorthand "in" applies to English only – in Afrikaans for example, the shorthand "dm" is used for the equivalent Afrikaans word "duim". Since both "in" and "dm" are contractions of the same word, but in different languages, they are abbreviations. A symbol on the other hand, defined as "Mark or character taken as the conventional sign of some object or idea or process" applies the appropriate shorthand by substitution rather than by contraction. Since the shorthand for kilometre (Quilômetro in Portuguese or Χιλιόμετρο in Greek) is "km" in both languages and the letter "k" does not appear in the expansion of either translation, "km" is a symbol as it is a substitution rather than a contraction.

In the International System of Units (SI) manual the word "symbol" is used consistently to define the shorthand used to represent the various SI units of measure. The manual also defines the way in which units should be written, the principal rules being:

• The conventions for upper and lower case letters must be observed – for example 1 MW (megawatts) is equal to 1,000,000,000 mW (milliwatts).
• No periods should be inserted between letters – for example "m.s" (which is an approximation of "m·s", which correctly uses middle dot) is the symbol for "metres multiplied by seconds", but "ms" is the symbol for milliseconds.
• No periods should follow the symbol unless the syntax of the sentence demands otherwise (for example a full stop at the end of a sentence).
• The singular and plural versions of the symbol are identical – not all languages use the letter "s" to denote a plural.