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an·cil·lar·y
ˈansəˌlerē

adjective
1.
providing necessary support to the primary activities or operation of an organization, institution, industry, or system.
“the development of ancillary services to support its products”

noun
1.
a person whose work provides necessary support to the primary activities of an organization, institution, or industry.
“the employment of specialist teachers and ancillaries”