hand typing

Drafting IEC publications



17 Symbols and abbreviated terms

17.1 Purpose or rationale

The symbols and abbreviated terms clause or subclause provides a list of the symbols and abbreviated terms used in the document, along with their definitions.


17.2 Normative or informative?

The symbols and abbreviated terms clause is a normative element.


17.3 Mandatory, conditional or optional?

The symbols and abbreviated terms clause is a conditional element.


17.4 Numbering and subdivision

It is not necessary to number the symbols. For convenience, the symbols and abbreviated terms may be combined with the terms and definitions in order to bring together terms and their definitions, symbols and abbreviated terms under an appropriate composite title, for example "Terms, definitions, symbols and abbreviated terms".


17.5 Specific principles and rules

Only symbols used in the text shall be listed.


Unless it is necessary to list symbols in a specific order to reflect technical criteria, all symbols should be listed in alphabetical order in the following sequence:

  • uppercase Latin letter followed by lowercase Latin letter (A, a, B, b, etc.);
  • letters without indices preceding letters with indices, and with letter indices preceding numerical ones (B, b, C, Cm, C2, c, d, dext, dint, d1, etc.);
  • Latin letters followed by Greek letters (Z, z, A, α, B, β, …, L, λ, etc.);
  • any other special symbols.