Two shapes are congruent if they are exactly the same size and shape. One can be moved, rotated, or reflected to fit perfectly on top of the other — no resizing allowed.
For triangles, there are reliable shortcuts to prove congruence without measuring everything: SSS (all three pairs of sides equal), SAS (two sides and the angle between them), ASA (two angles and the side between them).
Congruent shapes have all corresponding sides equal and all corresponding angles equal.
Remember
Congruent = identical. Same size, same shape. You can flip or rotate it, but you can't resize it.
Real World
Mass-produced parts in a factory are congruent — every bolt of the same model is identical in size and shape so they're interchangeable.
Feeling ready?
Put this concept to work with a practice workout.