In a general sense, the doing, executing or performing of any thing; discharge; performance; as the function of a calling or office. More generally,

Office or employment, or any duty or business belonging to a particular station or character, or required of a person in the station or character. Thus we speak of the functions of a chancellor, judge or bishop; the functions of a parent or guardian.

Trade; occupation.

The office of any particular part of animal bodies; the peculiar or appropriate action of a member or part of the body, by which the animal economy is carried on. Thus we speak of the functions of the brain and nerves, of the heart, of the liver, of the muscles.

Power; faculty, animal or intellectual. As the mind opens, and its functions spread.

In mathematics, the function of a variable quantity, is any algebraic expression into which that quantity enters, mixed with other quantities that have invariable values.