Function or functionality may refer to:

• Function key, a type of key on computer keyboards
• Function model, a structured representation of processes in a system
• Function object or functor or functionoid, a concept of object-oriented programming
• Function (computer programming), a callable sequence of instructions

• Function (music), a relationship of a chord to a tonal centre
• Function (musician) (born 1973), David Charles Sumner, American techno DJ and producer
• "Function" (song), a 2012 song by American rapper E-40 featuring YG, Iamsu! & Problem
• "Function", song by Dana Kletter from Boneyard Beach 1995

• Function (biology), the effect of an activity or process
• Function (engineering), a specific action that a system can perform
• Function (language), a way of achieving an aim using language
• Function (mathematics), a relation that associates an input to a single output
• Function (sociology), an activity's role in society
• Functionality (chemistry), the presence of functional groups in a molecule
• Party or function, a social event
• Function Drinks, an American beverage company

• Function field (disambiguation)
• Function hall
• Functional (disambiguation)
• Functional group (disambiguation)
• Functionalism (disambiguation)
• Functor (disambiguation)