The point about which an angle is measured is called the angle's vertex, and the angle θ associated with a given vertex is called the vertex angle. In a polygon, the (interior, i.e., measured on the interior side of the vertex) are generally denoted α_i or A_i. The sum of interior angles in any n-gon is given by (n - 2) π radians, or 2(n - 2)×90°.

angle | central angle | dihedral angle | exterior angle | line-line angle | regular polygon