| A | B |
|---|
| Collinear | points on the same line |
| Endpoints | A and B are the endpoints of AB where AB is the set of points A, B, and all the points between A and B |
| Line | A set of many points, that extend in opposite directions without ending |
| Line segment | Segment AB is the set of points A, B, and all the points between A and B |
| Plane | A two-dimensional flat surface |
| Point | A location in space represented by a dot |
| Ray | A set of points that is part of a line; a ray has one endpoint and extends in one direction with no end |
| Postulate | A statement accepted as true without proof |
| Angle | A figure made up of two sides, or rays, with a common endpoint |
| Bisect | To divide into two equal parts |
| Vertex | The point common to both sides of an angle |
| Acute angle | An angle whose measure is less than 90 degrees |
| Obtuse angle | an angle whose measure is greater than 90 degrees but less than 180 degrees |
| Perpendicular lines | Lines that form right angles |
| Right angle | An angle whose measure is 90 degrees |
| Straight angle | An angle whose measure is 180 degrees |
| Adjacent angles | Angles with a common vertex and one common side |
| Complementary angles | Two angles whose measures add to 90 degrees |
| Supplementary angles | Two angles whose measures add to 180 degrees |
| Vertical angles | Angles that have a common vertex and whose sides are formed by the same lines |
