"Congruent" is an adjective that describes a situation in which two or more concepts come together in agreement or harmony. This state is described as a congruence.
When the word "congruence" is used in mathematics or geometry, it refers to two objects being identical because their shapes correspond exactly to one another when overlapped. This relationship is represented by a tilde mark over an equals symbol. The word comes from Middle English with its origin in the Latin "congruens," which means "to meet together or agree." "Congruous" is a related word with the same meaning, but this word is not used in scientific writing.