functional

Etymology

function + -al

adj

1. In good working order.
2. Useful; serving a purpose, fulfilling a function
   That sculpture is not merely artistic, but also functional: it can be used as a hatrack.
3. Only for functional purposes, notably in architecture
   A functional construction element generally must meet higher technical but lower aesthetical requirements
4. (computing theory) Having semantics defined purely in terms of mathematical functions, without side-effects.
   ,
5. (medicine) Of a disease, such that its symptoms cannot be referred to any appreciable lesion or change of structure; opposed to organic disease, in which the organ itself is affected.

noun

1. (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.
   An example of a functional is the definite integration of integrable real functions in a real interval.
2. (mathematics, functional analysis) A scalar-valued linear function on a vector space.
3. (computing) An object encapsulating a function pointer (or equivalent).