1》 an activity that is natural to or the purpose of a person or thing.
↘a computer operation corresponding to a single instruction from the user.
2》 a large or formal social event or ceremony.
3》 Mathematics a relation or expression involving one or more variables.
↘a variable quantity regarded as depending on another variable.
4》 a thing dependent on another factor or factors.
5》 Chemistry a ~al group.
■ verb work or operate in a proper or particular way.
↘( ~ as ) fulfil the purpose or task of (a specified thing).
C16: from Fr. fonction , from L. functio(n-) , from fungi 'perform'.