the quality or state of corresponding, agreeing, or being congruent
2.
(maths) the relationship between two integers, x and y, such that their difference, with respect to another positive integer called the modulus, n, is a multiple of the modulus. Usually written x ≡ y (mod n), as in 25 ≡ 11 (mod 7)
mid-15c., from Latin congruentia "agreement, harmony, congruity," from congruentem (nominative congruens), present participle of congruere "to come together" (see congruent). Related: Congruency.