Definitions for "Adjoin"
To join or unite to; to lie contiguous to; to be in contact with; to attach; to append.
To lie or be next, or in contact; to be contiguous; as, the houses adjoin.
To join one's self.
Keywords:  lisp, add, lawyer, copy, letter
attach or add; "I adjoin a copy of your my lawyer's letter"
A LISP function that adds an element to a set if it is not already there.