A complement is something that completes something else. Complement may refer specifically to:

The arts

* Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-class collections into complementary sets * Complementary color, in the visual arts

Biology and medicine

Complement system The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and at ...

(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

Grammar and linguistics

Complement (linguistics) In grammar, a complement is a word, phrase, or clause that is necessary to complete the meaning of a given expression. Complements are often also arguments (expressions that help complete the meaning of a predicate). Predicative, subject and o ...

, a word or phrase having a particular syntactic role **

Subject complement In grammar, a subject complement or predicative of the subject is a predicative expression that follows a linking verb ( copula) and that complements the subject of the sentence by either (1) renaming it or (2) describing it. It completes the mea ...

, a word or phrase adding to a clause's subject after a linking verb * Phonetic complement *

Complementary A complement is something that completes something else. Complement may refer specifically to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-class ...

, a type of opposite in lexical semantics (sometimes called an antonym)

Mathematics

Algebra

Complement (group theory) In mathematics, especially in the area of algebra known as group theory, a complement of a subgroup ''H'' in a group ''G'' is a subgroup ''K'' of ''G'' such that :G = HK = \ \text H\cap K = \. Equivalently, every element of ''G'' has a unique expr ...

Complementary subspaces In abstract algebra, the direct sum is a construction which combines several modules into a new, larger module. The direct sum of modules is the smallest module which contains the given modules as submodules with no "unnecessary" constraints, ma ...

* Orthogonal complement *

Schur complement In linear algebra and the theory of matrices, the Schur complement of a block matrix is defined as follows. Suppose ''p'', ''q'' are nonnegative integers, and suppose ''A'', ''B'', ''C'', ''D'' are respectively ''p'' × ''p'', ''p'' × ''q'', ''q'' ...

Algorithms

* Complement (complexity), relating to decision problems and complexity classes *

Complement operator (regular expressions) A regular expression (shortened as regex or regexp; sometimes referred to as rational expression) is a sequence of Character (computing), characters that specifies a pattern matching, search pattern in String (computer science), text. Usually s ...

* Method of complements, in computer science ** Radix complement ** Diminished radix complement ** Ones' complement ** Two's complement

Discrete mathematics

* Complement graph ** Self-complementary graph, a graph which is isomorphic to its complement * Complemented lattice

Geometry

* Complementary angles *

Knot complement In mathematics, the knot complement of a tame knot ''K'' is the space where the knot is not. If a knot is embedded in the 3-sphere, then the complement is the 3-sphere minus the space near the knot. To make this precise, suppose that ''K'' is a ...

* Complement of a point, the dilation of a point in the centroid of a given triangle, with ratio −1/2

Logic

Complement (set theory) In set theory, the complement of a set , often denoted by (or ), is the set of elements not in . When all sets in the universe, i.e. all sets under consideration, are considered to be members of a given set , the absolute complement of is the ...

* Complementary event in probability * Logical complement *

Bitwise complement In computer programming, a bitwise operation operates on a bit string, a bit array or a binary numeral (considered as a bit string) at the level of its individual bits. It is a fast and simple action, basic to the higher-level arithmetic operati ...

* Complements in boolean algebra

Other uses

Complementary experiments In physics, two experimental techniques are often called complementary if they investigate the same subject in two different ways such that two different (ideally non-overlapping) properties or aspects can be investigated. For example, X-ray scatter ...

, in physics *

Complement good In economics, a complementary good is a good whose appeal increases with the popularity of its complement. Technically, it displays a negative cross elasticity of demand and that demand for it increases when the price of another good decreases. I ...

(economics), a good often consumed together with another good * Ship's complement, the number of persons in a ship's company