Two angles are congruent if they have the same measure.
Two figures are congruent if they have the same shape and size.
Two figures are similar if they have the same shape but not necessarily the same size.
These figures are congruent, since they all have the same shape and size.
These figures are NOT congruent. Although they are the same shape, they are different sizes. Figures that are the same shape but different in size are similar.
These two figures are NOT congruent, since they do not have the same shape.