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function

American  
[fuhngk-shuhn] / ˈfʌŋk ʃən /

noun

  1. the kind of action or activity proper to a person, thing, or institution; the purpose for which something is designed or exists; role.

  2. any ceremonious public or social gathering or occasion.

  3. a factor related to or dependent upon other factors.

    Price is a function of supply and demand.

  4. Mathematics.

    1. Also called correspondence, map, mapping, transformation.  a relation between two sets in which one element of the second set is assigned to each element of the first set, as the expression y = x 2 ; operator.

    2. Also called multiple-value function.  a relation between two sets in which two or more elements of the second set are assigned to each element of the first set, as y 2 = x 2 , which assigns to every x the two values y = + x and y = − x.

    3. a set of ordered pairs in which none of the first elements of the pairs appears twice.

    4. a relationship in which an input value of a variable has a specifically calculated output value: for example, if the function of x is x 2 , the output will always be the square of whatever the value of x is. f, F

  5. Geometry.

    1. a formula expressing a relation between the angles of a triangle and its sides, as sine or cosine.

    2. hyperbolic function.

  6. Grammar.

    1. the grammatical role a linguistic form has or the position it occupies in a particular construction.

    2. the grammatical roles or the positions of a linguistic form or form class collectively.

  7. Sociology. the contribution made by a sociocultural phenomenon to an ongoing social system.

verb (used without object)

  1. to perform a specified action or activity; work; operate.

    The computer isn't functioning now. He rarely functions before noon.

  2. to have or exercise a function; serve.

    In earlier English the present tense often functioned as a future. This orange crate can function as a chair.
function British  
/ ˈfʌŋkʃən /

noun

  1. the natural action or intended purpose of a person or thing in a specific role

    the function of a hammer is to hit nails into wood

  2. an official or formal social gathering or ceremony

  3. a factor dependent upon another or other factors

    the length of the flight is a function of the weather

  4. Also called: map.   mapping.  maths logic a relation between two sets that associates a unique element (the value) of the second (the range) with each element (the argument) of the first (the domain): a many-one relation. Symbol: f( x ) The value of f( x ) for x = 2 is f(2)

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

verb

  1. to operate or perform as specified; work properly

  2. (foll by as) to perform the action or role (of something or someone else)

    a coin may function as a screwdriver
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
function Scientific  
/ fŭngk′shən /

  1. A relationship between two sets that matches each member of the first set with a unique member of the second set. Functions are often expressed as an equation, such as y = x + 5, meaning that y is a function of x such that for any value of x, the value of y will be 5 greater than x.

  2. A quantity whose value depends on the value given to one or more related quantities. For example, the area of a square is a function of the length of its sides.

function Cultural  

  1. In mathematics, a quantity whose value is determined by the value of some other quantity. For example, “The yield of this field is a function of the amount of fertilizer applied” means that a given amount of fertilizer will yield an amount of whatever crop is growing.

Other Word Forms

  • functionless adjective
  • interfunction adjective
  • multifunction adjective
  • nonfunctioning adjective
  • overfunctioning adjective
  • prefunction noun
  • refunction verb (used without object)
  • subfunction noun
  • superfunction noun
  • unfunctioning adjective
  • well-functioning adjective

Etymology

Origin of function

First recorded in 1525–35; from Latin functiōn- (stem of functiō ) “a performance, execution,” equivalent to funct(us) (past participle of fungī ) “performed, executed” + -iōn- -ion

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

It is whether we are building a food system that can continue to function when they do.

From Science Daily • Apr. 5, 2026

For them, labor was a spiritual act, function guided form, beauty lay in simplicity, and well-designed objects need never change.

From The Wall Street Journal • Apr. 4, 2026

Marketers also claim thymosin-alpha, one of the more studied peptides, can help with immune function, Lyme disease and COVID-19.

From Salon • Apr. 4, 2026

"It's just making sure that the club has enough money to function and make sure that we actually get the job done."

From BBC • Apr. 3, 2026

“We had a function at my school this afternoon. For the debate team, and I was the first speaker.”

From "Amina's Song" by Hena Khan

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.