Merriam-Webster's Collegiate® Dictionary, 11th Edition
FUNCTION
I. noun
Etymology: Latin function-, functio performance, from fungi to perform; probably akin to Sanskrit bhuṅkte he enjoys
Date: 1533
professional or official position ; occupation , the action for which a person or thing is specially fitted or used or for which a thing exists ; purpose , any of a group of related actions contributing to a larger action, an official or formal ceremony or social gathering,
5. a mathematical correspondence that assigns exactly one element of one set to each element of the same or another set, a variable (as a quality, trait, or measurement) that depends on and varies with another , characteristic behavior of a chemical compound due to a particular reactive unit, a computer subroutine, functionless adjective Synonyms: see: function
II. intransitive verb (functioned; functioning)
Date: 1856
to have a function ; serve , to carry on a function or be in action ; operate