functional

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Of or relating to a function.
2. adj. Of, relating to, or indicating a mathematical function or functions.
3. adj. Designed for or adapted to a particular function or use: functional architecture.
4. adj. Capable of performing; operative: a functional set of brakes.
5. adj. Pathology Involving functions rather than a physiological or structural cause.
6. n. A linear function on vectors whose values are scalars.

Century Dictionary and Cyclopedia

1. Pertaining to functions; relating to some office or function.
2. Pertaining to an algebraical operation: as, a functional symbol.
3. Having the function usual to the part or organ: as, functional wings of an insect (that is, those used for flying).

Wiktionary

1. adj. In good working order.
2. adj. Useful; serving a purpose, fulfilling a function
3. adj. Only for fuctional purposes, notably in architecture
4. adj. Having semantics defined purely in terms of mathematical functions, without side-effects.
5. adj. 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.
6. n. 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 valued, complex valued) functions and whose value belongs to a monodimensional space. An example: the definite integration of integrable real functions in a real interval.

GNU Webster's 1913

1. adj. Pertaining to, or connected with, a function or duty; official.
2. adj. Pertaining to the function of an organ or part, or to the functions in general; involving or affecting function rather than physiology. See functional disease, below.
3. adj. Designed for or capable of a particular function or use.
4. adj. Fit or ready for use or service; useable; in working order. Antonym of out of order and nonfunctional.
5. adj. Designed to emphasize practical utility rather than artistic or aesthetic purposes.

WordNet 3.0

1. adj. (of e.g. a machine) performing or capable of performing
2. adj. fit or ready for use or service
3. adj. designed for or adapted to a function or use
4. adj. involving or affecting function rather than physiology
5. adj. designed for or capable of a particular function or use
6. adj. relating to or based on function especially as opposed to structure