| A | B |
|---|
| isosceles triangle | A triangle having two sides of equal length. |
| equilateral triangle | A triangle having all three sides of equal length |
| scalene triangle | A triangle having three sides of different lengths |
| line segment | A line segment does not extend forever, but has two distinct endpoints. |
| ray | a "straight" line that begins at a certain point and extends forever in one direction |
| parallel lines | Two lines in the same plane which never intersect are called parallel lines |
| polygon | A polygon is a closed figure made by joining line segments, where each line segment intersects exactly two others |
| vertex | The vertex of an angle is the point where the two rays that form the angle intersect. |
| quadrilateral | A four-sided polygon. The sum of the angles of a quadrilateral is 360 degrees |
| right angle | A right angle is an angle measuring 90 degrees |
| angle | Two rays that share the same endpoint form an angle |
| degree | We measure the size of an angle using degrees-one degree is 1/360 degrees |
