An Adjunct

1. An appendage; something attached to something else in a subordinate capacity.
2. A person associated with another, usually in a subordinate position; a colleague.
3. (brewing) An unmalted grain or grain product that supplements the main mash ingredient.
4. (dated, metaphysics) A quality or property of the body or mind, whether natural or acquired, such as colour in the body or judgement in the mind.
5. (music) A key or scale closely related to another as principal; a relative or attendant key.
6. (grammar) A dispensable phrase in a clause or sentence that amplifies its meaning, such as "for a while" in "I typed for a while".
7. (syntax, X-bar theory) A constituent which is both the daughter and the sister of an X-bar.
8. (rhetoric) Symploce.
9. (category theory) One of a pair of morphisms which relate to each other through a pair of adjoint functors.

(something attached to something else): addition, supplement

(person associated with another): associate (colleague) or attendant (subordinate)