Congruence

Mathematics

Congruence (geometry), being the same size and shape
Congruence or congruence relation, in abstract algebra, an equivalence relation on an algebraic structure that is compatible with the structure
In modular arithmetic, having the same remainder when divided by a specified integer
- Ramanujan's congruences, congruences for the partition function, Template:Math, 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

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

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