Congruence may refer to: 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, , 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 space time, 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#Incongruence Mood congruence between feeling or emotion (in psychiatry and psychology) Incongruity theory of humor See also Congruence bias, a type of cognitive bias, similar to confirmation bias Congruence principle (disambiguation) Hatch mark, geometric notation for congruent line segments ≅ ≡ (disambiguation) ≃