WordNet sense 1 (a mathematical relation such that each element of one set is associated with at least one element of another set):

mathematical function

WordNet sense 2 (a vaguely specified social event):

affair, occasion, social function, social occasion

WordNet sense 3 (a set sequence of steps, part of larger computer program):

procedure, routine, subroutine, subprogram

WordNet sense 4 (what something is used for):

purpose, role, use, use

WordNet sense 5 (serve a purpose, role, or function):

serve

WordNet sense 6 (perform as expected when applied):

go, operate, run, work

WordNet sense 7 (perform duties attached to a particular office or place or function):

officiate

WordNet sense 8 (the actions and activities assigned to or required or expected of a person or group):

office, part