Mathematics. of or relating to two numbers related by a congruence.
Geometry. coinciding at all points when superimposed: congruent triangles.
Origin of congruent
1375–1425;late Middle English < Latincongruent- (stem of congruēns, present participle of congruere to come together, fit in, agree), equivalent to con-con- + -gru- base of uncertain meaning (attested only in this v. and ingruere to fall upon) + -ent--ent
early 15c., "suitable, proper," from Latin congruentem (nominative congruens) "agreeing, fit, suitable," present participle of congruere, literally "to come together, agree, correspond with," from com- "with" (see com-) + a lost verb *gruere, *ruere "fall, rush," perhaps from PIE *ghrei- "to rub, grind" (see chrism). Geometry sense attested by 1706.