W: (v) function [Related to: functionary] (perform duties attached to a particular office or place or function) "His wife officiated as his private secretary"
S: (n) official (someone who administers the rules of a game or sport) "the golfer asked for an official who could give him a ruling"
Adjective
S: (adj) official (having official authority or sanction) "official permission"; "an official representative"
W: (adj) unofficial [Opposed to: official] (not having official authority or sanction) "a sort of unofficial mayor"; "an unofficial estimate"; "he participated in an unofficial capacity"