(Lat. congruo to agree), a suitableness or relation of agreement between things.

It is a matter of experience that congruity, wherever perceived, is agreeable; and that incongruity is disagreeable. The only difficulty is to ascertain what are the particular objects which in conjunction suggest these relations; for there are many objects that do not. The sea, for example viewed in conjunction with a picture, or a man viewed in conjunction with a mountain, suggests neither congruity nor incongruity. It seems natural to infer, what indeed will be found true by induction, that we never perceive congruity or incongruity except among things which are connected together by some relation; such as a man and his actions, a principal and his accessories, a subject and its ornaments. Congruity is so nearly allied to beauty as commonly to be regarded as a species of it; and yet they differ so essentially as never to coincide. Beauty, like colour, is placed upon a single subject; congruity upon a plurality; and a thing beautiful in itself may, with relation to other things, produce the strongest sense of incongruity.

Congruity is also to be distinguished from propriety; congruity being the genus of which propriety is a species.