something added to another thing but not essential to it.

a person associated with lesser status, rank, authority, etc., in some duty or service; assistant.

a person working at an institution, as a college or university, without having full or permanent status

My lawyer works two nights a week as an adjunct, teaching business law at the college.

Grammar . a modifying form, word, or phrase depending on some other form, word, or phrase, esp. an element of clause structure with adverbial function.

joined or associated, esp. in an auxiliary or subordinate relationship.

attached or belonging without full or permanent status

an adjunct surgeon on the hospital staff.

noun

detriment , lessening , subtraction

noun

accessory , addendum , appendage , appendix , appurtenance , associate , auxiliary , complement , detail , partner , subordinate , supplement , accompaniment , addition , additive , adjective , affix , annex , appanage , attachment , colleague , endowment , help , ornament , part , perquisite , quality , subsidiary , tangency