relative complement

relative complement (plural relative complements)

1. (set theory, of set A "in" set B) The set containing exactly those elements belonging to B but not to A.

• In mathematical expressions, the relative complement of A in B is denoted B ∖ A according to the ISO 31-11 standard (sometimes written B − A, but this notation is ambiguous, as in some contexts it can be interpreted as the set of all b − a, where b is taken from B and a from A).

• set-theoretic difference