| A | B |
|---|
| point | exact location in space |
| line | straight arrangement of points that extends forever in opposite directions |
| plane | flat surface that extends forever |
| line segment | part of a line that consists of two endpoints |
| ray | part of a line that has one endpoint and extends forever in one direction |
| angle | what is formed when two rays share a common endpoint |
| vertex | the endpoint of an angle |
| degree | unit that measures the size of an angle |
| protractor | tool used to measure angles |
| acute angle | less than 90 degrees |
| obtuse angle | more than 90 degrees |
| right angle | exactly 90 degrees |
| straight angle | equal to 180 degrees |
| complementary angles | the sum is 90 degrees |
| supplementary angles | the sum is 180 degrees |
| adjacent angles | two angles that share a common side |
| vertical angles | angles that are not adjacent when two lines intersect |
