Congruence is the most often used Geometric Property in reasoning and proofs. The word congruence is used to indicate the combined relationship of same shape and same size between geometrical figures. The congruence relationship is defined for basic ideas like line segments and angles and used in extending the concept to other geometric shapes.
Congruence is an idea equivalent to equality (=) in numerical expressions.

Congruence denotes the total agreement between geometric figures both in shape and size. Two or more shapes are said to be congruent if they are described by identical values in all the dimensions defining them.

This means their shapes agree in definition and in measurement as well.
Congruence is denoted by the symbol ≅.