| A | B |
|---|
| Line | extends forever in both directions |
| Segment | part of a line with two endpoints |
| Endpoint | a point at the end of a segment or ray |
| Intersect | lines that cross through the same point |
| Perpendicular | two lines that intersect at a right angle |
| Parallel | two lines, rays, or segments that do not cross no matter how far they extend |
| Angle | formed by two rays with the same endpoint |
| Side | each of the rays forming an angle |
| Vertex | the common endpoint of two rays forming an angle |
| Acute Angle | an angle smaller than a right angle |
| Right Angle | an angle like the corner of an index card. It measures 90 degrees. |
| Obtuse Angle | an angle greater than a right angle but smaller than a straight angle |
| Straight Angle | an angle formed by two rays pointing in the opposite direction |
| Degrees | a unit of angle measurement |
| Complementary Angles | two angles whose measures add up to 90 degrees |
| Supplementary Angles | two angles whose measures add up to 180 degrees |
| Protractor | a tool that measures angles |
| Ray | a part of a line that has one endpoint and extends forever in the other direction |
