functional
adj//ˈfʌŋkt͡ʃnəl//fungerande, funktionell, funktional
In good working order.
Useful; serving a purpose, fulfilling a function.
(computing theory) Having semantics defined purely in terms of mathematical functions, without side-effects.
(mathematics) A function that takes a function as its argument; more precisely, a function whose argument varies in a space of (real or complex valued) functions and whose value belongs to a monodimensional space.