A variable is an indefinite quantity expressed by a letter or symbol. Only variables are italic; words that designate mathematical functions (e.g., tan, cos, sin, tanh, cosh, sinh, log, ln) are roman.
All the variables presented in an equation/figure must be defined in the nomenclature. If not, the engineer must provide the definitions.
Variables are presented in two ways:
(a) Variables directly follow an equation and are introduced by the word "where," which is flush left and lowercase and not followed by a colon. See Sample.
(b) Variables are presented in a separate section. See Sample.
Order
The variables are listed alphabetically in the following order:
(a) uppercase letters
(b) lowercase letters
(c) Greek or other symbols
(d) subscripts
Uppercase, lowercase, Greek, and subscripts are integrated within the same letter. See Sample.
Definitions contain no end punctuation except if the text that follows the definition is a full sentence. Units of measure are abbreviated, preceded by a comma, at the end of the definition.
See Sample.
(a) Equal signs are aligned, with equal space around them.
(b) The word "or" generally appears between two equations and is set flush left and lowercase. It is not followed by a colon. See Sample.
