What is "congruency "? Well, 2 geometric objects are "congruent" if both their size and shape are identical.  For 2 triangles, this means the 2 triangles's corresponding angles and sides are equal.

 

Here are the conditions for determining if 2 triangles are congruent:

 

SSS rule: SSS refers to side, side, and side. Two triangles are congruent if three corresponding sides are equal.

 

SAS rule: SAS refers to side, angle, and side. Two triangles are congruent if two corresponding sides are equal and a corresponding angle between the sides are equal.

 

ASA rule: ASA refers to angle, side, and angle.  Two triangles are congruent if two corresponding angles are equal and one corresponding side is equal.