supernumerary

A person who works in a group, association, or public office without forming part of the regular staff (the numerary).

An extra or walk-on, often non-speaking, in a film or play; a spear carrier.

Something which is beyond the prescribed or standard amount or number.

An animal which has not formed a pair bond and is therefore single.

A married man or woman who is a secular member of Opus Dei, a Roman Catholic religious institution.