adj.1. a. Of or relating to a function.
b. Of, relating to, or indicating a mathematical function or functions.
2. Designed for or adapted to a particular function or use: functional architecture.
3. a. Capable of performing a function; operative: a functional set of brakes.
b. Able to function personally or socially despite limitations or impairment: a functional alcoholic.
4. Medicine Involving physiological function rather than anatomical structure.