an·cil·lar·y 
(ănsə-lĕr′ē)
(ănsə-lĕr′ē)adj.
1. Of secondary importance; subordinate: "For Degas, sculpture was never more than ancillary to his painting" (Herbert Read).
2. Auxiliary or accessory: an ancillary pump.
n. pl. an·cil·lar·ies
1. Something that is subordinate or accessory to something else: a tripod, battery charger, and other camera ancillaries.
2. A person working in a supportive or subordinate role: school ancillaries who look after children who become sick.
[From Latin ancilla, maidservant, feminine diminutive of anculus, servant; see kwel-1 in the Appendix of Indo-European roots.]