| A | B |
|---|
| acute triangle | A triangle whose largest angle measures less than 90°. |
| angle | The opening that is formed when two lines, line segments, or rays intersect. |
| congruent | Having the same size and shape. |
| hexagon | A polygon with six sides. |
| line of symmetry | A line that divides a figure into two halves that are mirror images of each other |
| obtuse triangle | A triangle whose largest angle measures more than 90° and less than 180°. |
| octagon | A polygon with eight sides. |
| pentagon | A polygon with five sides. |
| polygon | A closed, flat shape with straight sides. |
| quadrilateral | Any four-sided polygon. |
| regular polygon | A polygon in which all sides have equal lengths and all angles have equal measures. |
| right angle | An angle that forms a square corner and measures 90°. It is often marked with a small square. |
| right triangle | A triangle whose largest angle measures 90°. |
| similar | Having the same shape but not necessarily the same size. |
| straight angle | An angle that measures 180° and thus forms a straight line. |
| symmetry | Correspondence in size and shape on either side of a dividing line, |
| triangle | A polygon with three sides and three angles. |
| vertex | (Plural: vertices ) A point of an angle, polygon, or solid where two or more lines, rays, or segments meet. |
| isosceles triangle | A triangle with at least two sides of equal length and two angles of equal measure. |
| parallel lines | Lines that stay the same distance apart; lines that do not cross. |
| scalene triangle | A triangle with three sides of different lengths. |
| side | A line segment that is part of a polygon. |
| Vertical | Upright; perpendicular to horizontal. |
