\congThe symbol \cong is used to denote congruence, which is a relation indicating that two geometric figures or algebraic expressions are equivalent in shape and size, or that they satisfy certain modular arithmetic conditions.
Two triangles are congruent, meaning they have the same shape and size.
\triangle ABC \cong \triangle DEFIn modular arithmetic, two numbers are congruent if they have the same remainder when divided by a modulus.
a \equiv b \pmod{n} \Rightarrow a \cong b \pmod{n}Two angles are congruent, meaning they have the same measure.
\angle A \cong \angle B