Which word denotes something that is subordinate or supplementary?

The word that denotes something that is subordinate or supplementary is "ancillary." This term is often used to describe services, support, or items that are additional to the main function or purpose but still serve an important role in enhancing or complementing it. For example, in healthcare, ancillary services such as physical therapy or laboratory work support the primary medical treatment but are not the main focus.

In contrast, the other choices represent different concepts. "Principal" indicates something that is primary or of the highest importance, which is the opposite of being subordinate. "Mandatory" refers to something that is required or compulsory, rather than supplementary. "Integrative" suggests a combining or unifying aspect, which does not directly convey the idea of being subordinate or supplementary. Thus, "ancillary" accurately captures the essence of something that plays a supporting or subordinate role.