There are multiple definitions - click on the translation that matches your context.

annexe

full

ancillary

adjective

Definitions of ancillary

English

in addition to or connected with something, but less important

it was held that as s.62 was ancillary to s.10 under which licences were granted.

English

providing help or support to a professional person or an organisation

All educational establishments are dependent for their day-to-day running on the ancillary staff.