Complement

In many different fields, the complement of X is something that together with X makes a complete whole&mdash;something that supplies what X lacks.

Complement may refer to:


 * Complement (linguistics), a word or phrase having a particular syntactic role
 * Phonetic complement
 * Complementary, a type of opposite in lexical semantics (sometimes called an antonym)
 * Complement (music), an interval that when added to another spans an octave
 * Aggregate complementation (music), the separation of pitch-class collections into complementary sets
 * Complementary color, in painting and optics
 * Complement good, a good often consumed together with another good in economics
 * Ship's complement, the number of persons in a Ship's Company, including both commissioned officers and crew

Mathematics and physics
Complement has a variety of uses in mathematics:


 * Complement (set theory)
 * Complement graph
 * Complement (group theory)
 * Complement operator (regular expressions)
 * Complementary angles
 * Complementary event in probability
 * Complementary subspaces
 * Complement (complexity), relating to decision problems and complexity classes


 * Complements in Boolean algebra
 * Knot complement
 * Logical complement
 * Bitwise complement
 * Orthogonal complement
 * Method of complements, a method to compute addition and subtraction in mathematics
 * Complemented lattice
 * Schur complement
 * Complement of a point, the dilation of a point in the centroid of a given triangle, with ratio &minus;1/2
 * Complementary experiments, in physics
 * Complement, binary representations of negative values in computer science
 * One's complement
 * Two's complement

Biology and medicine

 * Complement system (immunology), a cascade of proteins in the blood that form part of innate immunity
 * Complementary DNA, DNA reverse transcribed from a mature mRNA template
 * Complementarity (molecular biology), a property whereby double stranded nucleic acids pair with each other
 * Complementation (genetics), a test to determine if independent recessive mutant phenotypes are caused by mutations in the same gene or in different genes