(intransitive) To have a function. / (intransitive) To carry out a function; to be in action.

(mathematics) A function that takes a function as its argument; More precisely: A function y=f(x) whose argument x varies in a space of (real or complex valued) functions and whose value belongs to a monodimensional space. An example is the definite integration of integrable real functions in a real interval.

(uncountable) The ability to do a task, performance, or execution; a set of functions that something is able or equipped to perform.

In good working order. / Useful; serving a purpose, fulfilling a function / Only for functional purposes, notably in architecture

What something does or is used for. / A professional or official position. / An official or social occasion. / Something which is dependent on or stems from another thing; a result or concomitant.

present participle of function

Action of the verb function. / Manner by which something functions; the workings.

Functional, working / (euphemistic, of a person) Mentally disabled but still able to survive in wider society.

plural of functionality

simple past tense and past participle of function