Incongruent

Incongruent is an adjective meaning not congruent; not in agreement, compatibility, or correspondence. It is used across fields to describe a mismatch between two entities that would normally align.

In geometry, incongruent describes figures that cannot be mapped onto each other by translation, rotation, or reflection. Congruent figures have identical size and shape; incongruent figures differ in size and/or shape. Thus two triangles may be similar but incongruent if their sizes differ.

In mineralogy and materials science, incongruent dissolution describes a process where a solid dissolves to form a solution of a different composition and leaves behind a residue of a different solid. This is contrasted with congruent dissolution, where the dissolved species match the original solid’s composition.

In psychology and cognitive science, incongruent conditions involve stimuli that conflict with an expected response, creating interference. The Stroop task is a classic example: the name of a color printed in an incongruent ink color slows responses and increases errors.

In everyday usage, incongruent can describe things that are out of place or incompatible with surrounding elements or expectations.

Etymology: from Latin incongruent-, from in- “not” + congruent-, from con- “together” and gruere “to come together.”

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