In the old "Schoolhouse Rock" song, "Conjunction junction, what's your function?," the word function means, "What does a conjunction do?" The famous design dictum "form follows function" tells us that an object's design should reflect what it does.

Function is one of those words that gets used a lot and means lots of different things. It means what something does, but also what a person does, whether something or someone is doing what they should, and crazily enough, a big party. "Your function is to bring the senator coffee at the political function. He cannot function without it."

Definitions of function
  1. noun
    what something is used for
    “the function of an auger is to bore holes”
    synonyms: purpose, role, use
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    raison d'etre
    the purpose that justifies a thing's existence
    type of:
    usefulness, utility
    the quality of being of practical use
  2. noun
    the actions and activities assigned to or required or expected of a person or group
    “the function of a teacher”
    synonyms: office, part, role
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    a specified function
    an informal term for a person's role
    the role of the head of a government department
    lieu, place, position, stead
    the post or function properly or customarily occupied or served by another
    second fiddle
    a secondary role or function
    as the agent of or on someone's part (usually expressed as "on behalf of" rather than "in behalf of")
    type of:
    work that you are obliged to perform for moral or legal reasons
  3. noun
    the normal physiological activity or action of a body part or organ
  4. verb
    serve a purpose, role, or function
    “The table functions as a desk”
    synonyms: serve
    serve, service
    be used by; as of a utility
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    serve as a prelude or opening to
    act as
    function as or act like
    type of:
    answer, do, serve, suffice
    be sufficient; be adequate, either in quality or quantity
  5. verb
    perform as expected when applied
    synonyms: go, operate, run, work
    be operating, running or functioning
    operate in or through
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    malfunction, misfunction
    fail to function or function improperly
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    do double duty; serve two purposes or have two functions
    begin operating or running
    be operating, running or functioning
    function as a cutting instrument
    serve, service
    be used by; as of a utility
  6. verb
    perform duties attached to a particular office or place or function
    synonyms: officiate
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    type of:
    do duty or hold offices; serve in a specific function
  7. noun
    a relation such that one thing is dependent on another
    “height is a function of age”
    “price is a function of supply and demand”
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    type of:
    an abstraction belonging to or characteristic of two entities or parts together
  8. noun
    (mathematics) a mathematical relation such that each element of a given set (the domain of the function) is associated with an element of another set (the range of the function)
    synonyms: map, mapping, mathematical function, single-valued function
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    multinomial, polynomial
    a mathematical function that is the sum of a number of terms
    a function expressed as a sum or product of terms
    inverse function
    a function obtained by expressing the dependent variable of one function as the independent variable of another; f and g are inverse functions if f(x)=y and g(y)=x
    Kronecker delta
    a function of two variables i and j that equals 1 when i=j and equals 0 otherwise
    metric, metric function
    a function of a topological space that gives, for any two points in the space, a value equal to the distance between them
    (mathematics) a function that changes the position or direction of the axes of a coordinate system
    a one-to-one mapping of one metric space into another metric space that preserves the distances between each pair of points
    (mathematics) a symbol or function representing a mathematical operation
    circular function, trigonometric function
    function of an angle expressed as a ratio of the length of the sides of right-angled triangle containing the angle
    threshold function
    a function that takes the value 1 if a specified function of the arguments exceeds a given threshold and 0 otherwise
    exponential, exponential function
    a function in which an independent variable appears as an exponent
    biquadratic, biquadratic polynomial, quartic polynomial
    a polynomial of the fourth degree
    homogeneous polynomial
    a polynomial consisting of terms all of the same degree
    monic polynomial
    a polynomial in one variable
    quadratic, quadratic polynomial
    a polynomial of the second degree
    (mathematics) the sum of a finite or infinite sequence of expressions
    (mathematics) a transformation in which the direction of one axis is reversed
    (mathematics) a transformation in which the coordinate axes are rotated by a fixed angle about the origin
    (mathematics) a transformation in which the origin of the coordinate system is moved to another position but the direction of each axis remains the same
    affine transformation
    (mathematics) a transformation that is a combination of single transformations such as translation or rotation or reflection on an axis
    linear operator
    an operator that obeys the distributive law: A(f+g) = Af + Ag (where f and g are functions)
    identity, identity element, identity operator
    an operator that leaves unchanged the element on which it operates
    sin, sine
    ratio of the length of the side opposite the given angle to the length of the hypotenuse of a right-angled triangle
    arc sine, arcsin, arcsine, inverse sine
    the inverse function of the sine; the angle that has a sine equal to a given number
    cos, cosine
    ratio of the adjacent side to the hypotenuse of a right-angled triangle
    arc cosine, arccos, arccosine, inverse cosine
    the inverse function of the cosine; the angle that has a cosine equal to a given number
    tan, tangent
    ratio of the opposite to the adjacent side of a right-angled triangle
    arc tangent, arctan, arctangent, inverse tangent
    the inverse function of the tangent; the angle that has a tangent equal to a given number
    cotan, cotangent
    ratio of the adjacent to the opposite side of a right-angled triangle
    arc cotangent, arccotangent, inverse cotangent
    the inverse function of the cotangent; the angle that has a cotangent equal to a given number
    sec, secant
    ratio of the hypotenuse to the adjacent side of a right-angled triangle
    arc secant, arcsec, arcsecant, inverse secant
    the inverse function of the secant; the angle that has a secant equal to a given number
    cosec, cosecant
    ratio of the hypotenuse to the opposite side of a right-angled triangle
    arc cosecant, arccosecant, inverse cosecant
    the angle that has a cosecant equal to a given number
    (mathematics) a transformation that changes the size of a figure but not its shape
    type of:
    mathematical relation
    a relation between mathematical expressions (such as equality or inequality)
  9. noun
    a formal or official social gathering or ceremony
    “it was a black-tie function
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    type of:
    social affair, social gathering
    a gathering for the purpose of promoting fellowship
  10. noun
    a vaguely specified social event
    “a seemingly endless round of social functions
    synonyms: affair, occasion, social function, social occasion
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    an occasion on which people can assemble for social interaction and entertainment
    celebration, jubilation
    a joyful occasion for special festivities to mark some happy event
    ceremonial, ceremonial occasion, ceremony, observance
    a formal event performed on a special occasion
    a social function that is held for the purpose of raising money
    photo op, photo opportunity
    an occasion that lends itself to (or is deliberately arranged for) taking photographs that provide favorable publicity for those who are photographed
    an occasion of spending a night away from home or having a guest spend the night in your home (especially as a party for children)
    bash, brawl, do
    an uproarious party
    birthday party
    a party held on the anniversary of someone's birth
    bun-fight, bunfight
    (Briticism) a grand formal party on an important occasion
    an informal social gathering at which there is Scottish or Irish folk music and singing and folk dancing and story telling
    cocktail party
    an afternoon party at which cocktails are served
    a party for social dancing
    feast, fete, fiesta
    an elaborate party (often outdoors)
    house party
    a party lasting over one or more nights at a large house
    a happy party
    tea party
    a party at which tea is served
    whist drive
    a progressive whist party
    formal ceremony about important occasions
    a ceremony at which a dead person is buried or cremated
    hymeneals, nuptials, wedding, wedding ceremony
    the social event at which the ceremony of marriage is performed
    pageant, pageantry
    a rich and spectacular ceremony
    a ceremony in which something (as a building) is dedicated to some goal or purpose
    a ceremony accompanying the start of some enterprise
    commemoration, memorialisation, memorialization
    a ceremony to honor the memory of someone or something
    military ceremony
    a formal ceremony performed by military personnel
    induction, initiation, installation
    a formal entry into an organization or position or office
    (usually plural) a ceremony that involves processions and speeches
    fire walking
    the ceremony of walking barefoot over hot stones or a bed of embers
    formalities, formality
    a requirement of etiquette or custom
    a public ceremony on Maundy Thursday when the monarch distributes Maundy money
    a ceremonial feast held by some Indians of the northwestern coast of North America (as in celebrating a marriage or a new accession) in which the host gives gifts to tribesmen and others to display his superior wealth (sometimes, formerly, to his own impoverishment)
    type of:
    social event
    an event characteristic of persons forming groups
  11. noun
    a set sequence of steps, part of larger computer program
    synonyms: procedure, routine, subprogram, subroutine
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    cataloged procedure
    a set of control statements that have been placed in a library and can be retrieved by name
    contingency procedure
    an alternative to the normal procedure; triggered if an unusual but anticipated situation arises
    library routine
    a debugged routine that is maintained in a program library
    random number generator
    a routine designed to yield a random number
    recursive routine
    a routine that can call itself
    reusable routine
    a routine that can be loaded once and executed repeatedly
    executive routine, supervisory routine
    a routine that coordinates the operation of subroutines
    tracing routine
    a routine that provides a chronological record of the execution of a computer program
    service routine, utility routine
    a routine that can be used as needed
    dump routine
    a routine that writes from an internal store to some external medium
    input routine
    a routine that writes from an external source to an internal store
    output routine
    a routine that controls an output device
    type of:
    computer software, package, software, software package, software program, software system
    (computer science) written programs or procedures or rules and associated documentation pertaining to the operation of a computer system and that are stored in read/write memory
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