Angle - A figure formed by two rays with a common endpoint

Measure of an angle - the smallest amount of rotation about the vertex from one ray to the other, measured in degrees

Degrees - a unit for measuring angles

Congruent - having the same size and the same shape.

Sides of an angle - the rays of an angle

Angle addition - If point D is in the interior of ∠CAB, then m∠CAD + m∠DAB = m∠CAB.

Angle bisector - a ray that contains the vertex of an angle and divides the angle into two congruent angles

Incoming and outgoing angles - an angle in pool formed by the cushion and the path of the ball approaching and leaving the cushion

Reflex measure of an angle - the largest amount of rotation less than 360 degrees between the two rays that form the angle

Vertex - The common endpoint of an angle

Protractor - A geometry tool used to measure and draw angles.

Adjacent Angles - Angles that share a vertex and a side

Parallel lines - coplanar lines that never intersect

Perpendicular lines - lines that intersect at right angles

Skew lines - Lines that do not intersect and are not coplanar

Right angle - an angle that measures 90 degrees

Acute angle - an angle that measures less than 90 degrees

Obtuse angle - An angle that measures more than 90 degrees but less than 180 degrees

Complementary angles - Two angles whose sum is 90 degrees

Supplementary angles - two angles whose sum is 180 degrees.

Vertical angles - angles formed by intersecting lines that share a common vertex but not a common side

Linear pair of angles - two angles that share a vertex, a common side, and their non-common sides form a line.