Congruence

Congruence may refer to:

Mathematics

 * Congruence (geometry), being the same size and shape
 * In modular arithmetic, having the same remainder when divided by a specified integer
 * Ramanujan's congruences, congruences for the partition function, $p(n)$, first discovered by Ramanujan in 1919
 * Congruence subgroup, a subgroup defined by congruence conditions on the entries of a matrix group with integer entries
 * Congruence of squares, in number theory, a congruence commonly used in integer factorization algorithms
 * Matrix congruence, an equivalence relation between two matrices
 * Congruence (manifolds), in the theory of smooth manifolds, the set of integral curves defined by a nonvanishing vector field defined on the manifold
 * Congruence (general relativity), in general relativity, a congruence in a four-dimensional Lorentzian manifold that is interpreted physically as a model of spacetime or a bundle of world lines
 * Zeller's congruence, an algorithm to calculate the day of the week for any date
 * Scissors congruence, related to Hilbert's third problem

Mineralogy and chemistry
In mineralogy and chemistry, the term congruent (or incongruent) may refer to:


 * Congruent dissolution: substances dissolve congruently when the composition of the solid and the dissolved solute stoichiometrically match
 * Congruent melting occurs during melting of a compound when the composition of the liquid that forms is the same as the composition of the solid
 * Incongruent transition, in chemistry, is a mass transition between two phases which involves a change in chemical composition

Psychology

 * In Carl Rogers' personality theory, the compliance between ideal self and actual self-see Carl Rogers
 * Mood congruence between feeling or emotion (in psychiatry and psychology)
 * Incongruity theory of humor