Definition:Congruence (Geometry)

Definition
In the field of Euclidean geometry, two geometric figures are congruent if they are, informally speaking, both "the same size and shape".

That is, one figure can be overlaid on the other figure with a series of rotations, translations, and reflections.

Specifically:
 * all corresponding angles of the congruent figures must have the same measurement
 * all corresponding sides of the congruent figures must be be the same length.

Also see

 * Triangle Side-Angle-Side Equality
 * Triangle Side-Side-Side Equality
 * Triangle Angle-Angle-Side Equality
 * Triangle Angle-Side-Angle Equality