Triangle similarity refers to the concept that two triangles are similar if their corresponding angles are equal and their sides are in proportion. This means that the shape of the triangles is the same, but their sizes may differ. For example, if one triangle has angles of 30°, 60°, and 90°, any other triangle with the same angles will be similar, regardless of its size. There are several criteria to determine triangle similarity, including the Angle-Angle (AA) criterion, where two angles of one triangle are equal to two angles of another triangle. Another is the Side-Side-Side (SSS) similarity criterion, which states that if the sides of two triangles are proportional, the triangles are similar.