Definition:Complement


 * Geometry:
 * Complementary angles: two angles whose measures add up to the measure of a right angle.
 * Complements of Parallelograms: The extra bits that need to be added to a pair of parallelograms sharing a line for their diagonals that need to be added to make one big parallelogram.


 * Relation Theory:
 * Complement of Relation: for a relation $\mathcal R$, its complement is all those pairs which are not in $\mathcal R$.


 * Set Theory:
 * Set Complement or Relative Complement: two related concepts: all the elements of a set which are not in a given subset.


 * Logic:
 * Logical Complement: In logic, the negation of a statement.


 * Lattice Theory:
 * Complement of Lattice Element: An in a strong and precise sense incomparable element of an element of a bounded lattice.


 * Graph Theory:
 * Complement of Graph: a graph with the same vertex set but whose edge set is all those edges not in that graph.