Definitions of functional:

• adjective:   designed for or adapted to a function or use

  Example: "Functional education selects knowledge that is concrete and usable rather than abstract and theoretical"

• adjective:   fit or ready for use or service

  Example: "The toaster was still functional even after being dropped"

• adjective:   relating to or based on function especially as opposed to structure

  Example: "It is a functional one"

• adjective:   designed for or capable of a particular function or use

  Example: "A style of writing in which every word is functional"

• adjective:   involving or affecting function rather than physiology

  Example: "Functional deafness"

• adjective:   (of e.g. a machine) performing or capable of performing

  Example: "A functional set of brakes"