• Complement (linguistics)
  Complement (linguistics)
  In grammar the term complement is used with different meanings. The primary meaning is a word, phrase or clause that is necessary in a sentence to complete its meaning. We find complements that function as an argument and complements that exist within arguments.Both complements and modifiers add...
  
  , a word or phrase having a particular syntactic role
• Phonetic complement
  Phonetic complement
  A phonetic complement is a phonetic symbol used to disambiguate word characters that have multiple readings, in mixed logographic-phonetic scripts such as Egyptian hieroglyphs, Akkadian cuneiform, Japanese, and Mayan...
  
  
• Complementary, a type of opposite in lexical semantics (sometimes called an antonym)
• Complement (music)
  Complement (music)
  In music the term complement refers to two distinct concepts.In traditional music theory a complement is the interval which, when added to the original interval, spans an octave in total. For example, a major 3rd is the complement of a minor 6th. The complement of any interval is also known as its...
  
  , an interval that when added to another spans an octave
• Aggregate complementation (music), the separation of pitch-class collections into complementary sets
• Complementary color
  Complementary color
  Complementary colors are pairs of colors that are of “opposite” hue in some color model. The exact hue “complementary” to a given hue depends on the model in question, and perceptually uniform, additive, and subtractive color models, for example, have differing complements for any given color.-...
  
  , in painting and optics
• Complement good
  Complement good
  A complementary good, in contrast to a substitute good, is a good with a negative cross elasticity of demand. This means a good's demand is increased when the price of another good is decreased. Conversely, the demand for a good is decreased when the price of another good is increased...
  
  , a good often consumed together with another good in economics
• Ship's complement, the number of persons in a Ship's Company
  Ship's Company
  The Ship's Company refers to all officers, non-commissioned officers and enlisted personnel aboard a naval vessel. The size of the ship's company is the number of people on board, excluding civilians and guests.-Command structure:...
  
  , including both commissioned officers and crew

Mathematics and physics

• Complement (set theory)
  Complement (set theory)
  In set theory, a complement of a set A refers to things not in , A. The relative complement of A with respect to a set B, is the set of elements in B but not in A...
  
  
• Complement graph
  Complement graph
  In graph theory, the complement or inverse of a graph G is a graph H on the same vertices such that two vertices of H are adjacent if and only if they are not adjacent in G. That is, to generate the complement of a graph, one fills in all the missing edges required to form a complete graph, and...
  
  
• Complement (group theory)
• Complement operator (regular expressions)
• Complementary angles
  Complementary angles
  In geometry, complementary angles are angles whose measures sum to 90°. If the two complementary angles are adjacent their non-shared sides form a right angle....
  
  
• Complementary event
  Complementary event
  In probability theory, the complement of any event A is the event [not A], i.e. the event that A does not occur. The event A and its complement [not A] are mutually exclusive and exhaustive. Generally, there is only one event B such that A and B are both mutually exclusive and...
  
   in probability
• Complementary subspaces
• Complement (complexity)
  Complement (complexity)
  In computational complexity theory, the complement of a decision problem is the decision problem resulting from reversing the yes and no answers. Equivalently, if we define decision problems as sets of finite strings, then the complement of this set over some fixed domain is its complement...
  
  , relating to decision problems and complexity classes

• Complements in Boolean algebra
• Knot complement
  Knot complement
  In mathematics, the knot complement of a tame knot K is the complement of the interior of the embedding of a solid torus into the 3-sphere. To make this precise, suppose that K is a knot in a three-manifold M. Let N be a thickened neighborhood of K; so N is a solid torus...
  
  
• Logical complement
• Bitwise complement
• Orthogonal complement
• Method of complements
  Method of complements
  In mathematics and computing, the method of complements is a technique used to subtract one number from another using only addition of positive numbers. This method was commonly used in mechanical calculators and is still used in modern computers...
  
  , a method to compute addition and subtraction in mathematics
• Complemented lattice
  Complemented lattice
  In the mathematical discipline of order theory, a complemented lattice is a bounded lattice in which every element a has a complement, i.e. an element b satisfying a ∨ b = 1 and a ∧ b = 0....
  
  
• Schur complement
  Schur complement
  In linear algebra and the theory of matrices,the Schur complement of a matrix block is defined as follows.Suppose A, B, C, D are respectivelyp×p, p×q, q×p...
  
  
• Complement of a point, the dilation of a point in the centroid
  Centroid
  In geometry, the centroid, geometric center, or barycenter of a plane figure or two-dimensional shape X is the intersection of all straight lines that divide X into two parts of equal moment about the line. Informally, it is the "average" of all points of X...
  
   of a given triangle, with ratio −1/2
• Complementary experiments
  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 properties or aspects can be investigated...
  
  , in physics
• Complement, binary representations of negative values in computer science
  • Ones' complement
  • Two's complement
    Two's complement
    The two's complement of a binary number is defined as the value obtained by subtracting the number from a large power of two...
    
    

Biology and medicine

• Complement system
  Complement system
  The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime...
  
   (immunology), a cascade of proteins in the blood that form part of innate immunity
• Complementary DNA
  Complementary DNA
  In genetics, complementary DNA is DNA synthesized from a messenger RNA template in a reaction catalyzed by the enzyme reverse transcriptase and the enzyme DNA polymerase. cDNA is often used to clone eukaryotic genes in prokaryotes...
  
  , DNA reverse transcribed from a mature mRNA template
• Complementarity (molecular biology)
  Complementarity (molecular biology)
  In molecular biology, complementarity is a property of double-stranded nucleic acids such as DNA, as well as DNA:RNA duplexes. Each strand is complementary to the other in that the base pairs between them are non-covalently connected via two or three hydrogen bonds...
  
  , a property whereby double stranded nucleic acids pair with each other
• Complementation (genetics)
  Complementation (genetics)
  In genetics, complementation refers to a relationship between two different strains of an organism which both have homozygous recessive mutations that produce the same phenotype . These strains are true breeding for their mutation...
  
  , a test to determine if independent recessive mutant phenotypes are caused by mutations in the same gene or in different genes