The grammatical relation of a word or phrase to a predicate

(linguistics) a distribution of related speech sounds or forms in such a way that they only appear in different contexts

In set theory, the complement of a set A, often denoted by A∁, is the set of elements not in A.When all elements in the universe, i.e. all elements under consideration, are considered to be members of a given set U, the absolute complement of A is the set of elements in U that are not in A. The relative complement of A with respect to a set B, also termed the set difference of B and A, written B ∖ A, {\displaystyle B\setminus A,} is the set of elements in B that are not in A.

A lattice is an abstract structure studied in the mathematical subdisciplines of order theory and abstract algebra.

Complementation refers to a genetic process when two strains of an organism with different homozygous recessive mutations that produce the same mutant phenotype have offspring that express the wild-type phenotype when mated or crossed.

In music theory, complement refers to either traditional interval complementation, or the aggregate complementation of twelve-tone and serialism.