adjunct

furnishing added support; "an ancillary pump"; "an adjuvant discipline to forms of mysticism"; "The mind and emotions are auxiliary to each other"

of or relating to a person who is subordinate to another

something added to another thing but not an essential part of it

a person who is an assistant or subordinate to another

a construction that can be used to extend the meaning of a word or phrase but is not one of the main constituents of a sentence