n. Suitableness or appropriateness of one thing to another; agreement; consistency. Also congruency.n. Tn mathematics, a relation between three numbers such that the difference between two of them, which are said to be congruent, is divisible by the third, which is called the modulus.n. In grammar, concord; agreement.n. Same as congruency, 2.n. In geometry, identity in shape and size. Its symbol is ≡.n. In line geometry, a set of ∞ lines, such that any two given conditions determine a definite finite number of lines of the set.