- Acute: less than 90
^{o} - Adjacent Angles: two coplanar angles with a common side, a common vertex, and no common interior points.
- Central Angle of a Circle
- Complementary: two angles whose sum is 90°
- Inscribed Angle of a Circle
- Linear Pair of Angles: angles that are supplementary and adjacent
- Obtuse: more than 90
^{o} - Supplementary: two angles that add up to 180
^{o} -
Parallel Line Angles: angles formed by Intersecting lines (corresponding, alternate interior, alternate exterior, same side interior)
- Interactive Parallel Lines Cut by a Transversal (and all the angles: corresponding, alternate interior and exterior)

- Triangle's Angles
- Right Angles: exactly 90°
- Vertical Angles
- Supplementary Angles
- Angles Associated with More Complex Shapes
- Angles and Circles
- Angles Formed by Intersection of Secants, Tangents Outside of a Circle