What a system should be able to do, the functions it should perform.
This term is used at both the user requirements analysis and software requirements specifications phases in the software life-cycle.
An example of a non-functional requirement is an initialisation sequence incorporated into the software that is specific to a given customer.
- Functional residual capacity
functional residual capacity n. Abbr. FRC The volume of gas remaining in the lungs at the end of a normal expiration. Also called functional residual air.
noun, Linguistics. 1. the organization of a sentence in terms of the role of its elements in distinguishing between old and new information, especially the division of a sentence into theme and rheme.
noun 1. a change in the grammatical function of a word, as in the use of the noun input as a verb or the noun fun as an adjective.
- Functional specification
programming, project A description of what a system (e.g. a piece of software) does or should do (but not how it should do it). The functional specification is one of the inputs to the design process. See IEEE/ANSI Std. 610.12-1990. (1999-04-07)