Difference Between Similarity and Congruence

The terms "similarity" and "congruence" have distinct meanings in geometry.

• Similarity
  Two figures are similar if they have the same shape but different sizes.

  For example, these two triangles are similar because they are both isosceles triangles, but they differ in size.
  

• Congruence
  Two geometric figures are congruent if they can be exactly matched point for point through a rigid transformation (e.g., rotation, translation, reflection).

  For instance, these two triangles are congruent because they have the same shape and size and can be perfectly aligned point for point after a rotation and translation.
  

And so on.