Ancillary - auxiliary
These two words have similar meanings, and can be found in similar contexts. However, their meanings are distinct. So is their spelling. The first ancillary has two '-l-s'. The second, auxiliary, has only one.
- ancillary (with two ‘-l-’s) is derived from the Latin word for a maidservant - ancilla. So it is used in the sense ‘supporting’ or ‘not important’, or ‘secondary’.
- auxiliary (with one ‘-l-’) derives from the Latin word for ‘help’ or ‘assistance’ - auxilium. In military terms, it denoted - and still denotes - soldiers who are not central to the action, although they may have an important role: in the Roman army, these were those non-citizen or mercenary forces fighting beside the Roman citizens in the Legions (regular troops|). For example: “the auxiliary forces [or auxiliaries] guarded the wings while the army marched”, or “Auxiliary vessels scouted the sea for any sign of the enemy”. In general use, it means ‘helping’, or ‘second rank’. Auxiliary nurses are usually less highly trained, and do less skilled jobs, than full nurses.
It is in technical areas that the words are most distinct. Sailing boats may have an auxiliary engine, for use when there is no wind; they do not have
ancillary engines. In English grammar, main verbs are helped to express their tenses, moods and voices by auxiliary verbs.