| Term | Definition |
| metric | centimeter is an example of length |
| line | lowercase script letter |
| collinear | Points on the same line |
| line segment | it has two endpoints and can be measured |
| supplementary | Two angles whose measures have a sum of 180° |
| customary | inch is an example of length |
| ray | one endpoint and extends indefinitely in one direction |
| obtuse | angle that measures between 90° and 180° |
| coplanar | Points on the same plane |
| plane | represented by a capital script letter |
| vertical | Two nonadjacent angles formed by two intersecting lines |
| vertex | common endpoint of an angle |
| perpendicular | lines that form right angles |
| complementary | Two angles whose measures have a sum of 90° |
| acute | angle that measures between 0° and 90° |
| linear pair | two adjacent angles whose opposite sides form a line |
| right | angle that measures 90° |
| bisect | cuts into two equal pieces |
| perpendicular | coplanar lines whose two slopes product is -1 |
| point | represented by a capital letter |
| parallel | coplanar lines that do not intersect |
| slope-intercept form | y=mx + b |
| point-slope form | y -y1 = m(x - x1) |