Adjunct is a constituent in an adjoined position.
- "Adjuncts (of place, time, manner, reason, etc....) are optional, or structurally dispensable, constituents of the sentence: they may be removed without affecting the remainder of the sentence." (Lyons 1968:334)
In [X Y [X ...]] Y is Chomsky -adjoined to X.
(i) John killed Bill in Central Park on Sunday.
(ii) John killed Bill in Central Park.
(iii) John killed Bill.
Usually the term 'adjunct' refers to base-generated adjuncts only.
Lyons, John. 1968. Introduction to Theoretical Linguistics. Cambridge: Cambridge University Press.