The adjective ancillary originally meant “relating to maidservants” from the Latin, but the element of a female servant has fallen away and now the word merely refers to a position as helpful or subordinate. An example of how something in medicine can be ancillary is after you have surgery you may also take a drug to aid healing — the drug would be considered ancillary to the surgery. One could also argue that in the United States the vice-president takes an ancillary role to the president.