| A | B |
|---|
| ray | a point on a line and all the points on one side of the point |
| angle | two rays having a common endpoint |
| vertex | the common endpoint of two rays in an angle |
| degree | a unit of measure of an angle |
| protractor | the instrument for measuring angles |
| congruent angles | angles with the same measure |
| acute angle | an angle of less than 90 degrees |
| right angle | an angle of exactly 90 degrees |
| obtuse angle | an angle that is more than 90 but less than 180 degrees |
| straight angle | an angle that is exactly 180 degrees |
