An angle is denoted by the angle symbol followed by three letters which represent points that form the angle. For example, the expression means “the angle formed by the points , and ” where the vertex of the angle is at the point .

The figure below also illustrates the angle

Congruent angles are denoted with tick marks across the angle.

Complementary angles can visually be denoted as two angles who sum to a perpendicular or square angle.

Supplementary angles can visually be denoted as two angles who sum to 180 degrees or PI degrees.