An angle marker is a mark drawn inside an angle to identify the angle or indicate its measure or geometric congruence with another angle. It commonly takes the form of a small circular arc centered at the vertex and joining the two rays that form the angle (Key Curriculum Press).
Matching patterns of arcs indicate congruent angles. One circular arc can mark one group, two arcs another, and three arcs a third (ACCESS Virtual Learning). The number of arcs labels a group and does not specify a numerical measure or a multiple of another angle. Different marking patterns alone do not assert that the corresponding angles have unequal measures.
An alternative convention uses a single circular arc crossed by one or more short hatch marks, also called tick marks. Angles with the same number of these marks are indicated to be congruent (Fallow and Griffiths 2009, p. 30). This use of a hatch mark is analogous to its use for equal-length line segments.
A right angle is commonly indicated by a small square called a right-angle marker.
