| A | B |
|---|
| parallel lines | lines in the same plane that do not intersect |
| acute angle | an angle with measure greater than 0 degrees and less than 90 degrees |
| point | an exact location in space |
| line | straight arrangement of points that extends forever in opposite directions |
| plane | a flat surface that extends forever |
| collinear | many points that lie on the same line |
| intersect | to meet or cross each other at one point |
| line segment | a part of a line that consists of two endpoints and all the points in between |
| endpoint | a point at the beginning or end of a part of a line |
| ray | a part of a line that has one endpoint and extends forever in one direction |
| angle | the figure formed when two rays share a common endpoint |
| vertex | the endpoint of the rays that form an angle |
| perpendicular lines | two lines intersect to form right angles |
| right angle | an angle with measure equal to 90 degrees |
| obtuse angle | an angle with measure greater than 90 degrees and less than 180 degrees |
| straight angle | an angle with measure equal to 180 degrees |
| complementary angles | two angles for which the sum of their measures is 90 degrees |
| supplementary angles | two angles for which the sum of their measures is 180 degrees |
| adjacent angles | two angles that share a common side but do not overlap each other |
| vertical angles | when two lines intersect, the angles that are not adjacent, but are always equal in measure |
