Ray: part of a line that starts at an endpoint and goes on
forever in one direction.
Two points on it identify a ray. Always name the endpoint first.
The symbol for a ray is an arrow above the two points - MN
Angle: figure formed by two rays with a common endpoint called a
It can be identified three ways: <EDF, <FDE, or <D (Note the letter of
the vertex is always in the middle)
Vertex: The common endpoint where two rays meet to form an angle
Degree: unit of measure that is
complete turn (circle)
Right angle: angle whose measure is equal to 90°.
Straight angle: angle whose measure is equal to 180° (A straight
Acute angle: angle whose measure is greater than 0° but less than
Obtuse angle: angle whose measure is greater than 90° but less
Supplementary angle: Two angles are supplementary angles if the
sum of the measures of the angles is 180°. (Add up to a straight line (S
<XYZ and <ZYW are supplementary
Complementary angles: Two angles are complimentary angles if the
sum of the measures of the angles is 90°. (C for Corner)
<ABC and <DBC are complementary