We say triangle ABC is congruent to triangle DEF if

both have same shape and size

Explanation

Two geometric figures are congruent if they have the same shape and size. For example, if △ABC and △DEF shown above are congruent, we can write

△ABC ≅ △DEF

Which reads as Triangle ABC is congruent to triangle DEF.

This means

• A ↔ D Read as “Point A corresponds to point D.”
• C ↔ F Read as “Point C corresponds to point F.”
• B ↔ E Read as “Point B corresponds to point E.”