| Term | Definition |
|---|
| acute angle | An angle that measures less than 90 degrees. |
| acute triangle | A triangle with all angles measuring less than 90 degrees. |
| angle | A figure formed by two rays sharing a common endpoint called the vertex. |
| complementary angle | Two angles whose measures add to 90 degrees. |
| congruent | Figures with the same size and shape. |
| correspondence | The relationship between two or more objects that are matched. |
| equilateral triangle | A triangle with three congruent sides. |
| isoscleles triangle | A triangle with at least two congruent sides. |
| line | A straight path that extends without end in opposite directions. |
| line symmetry | One half of a figure is a mirror image of the other half. |
| line of symmetry | The imaginary line drawn down the center of a figure with line symmetry. |
| obtuse angle | An angle whose measure is greater than 90 degrees. |
| obtuse triangle | A triangle containing one obtuse angle. |
| parallel lines | Lines in a plane that never intersect. |
| parallelogram | A quadrilateral with two pairs of parallel sides. |
| perpendicular lines | Lines that intersect to form right angles. |
| plane | A flat surface that extends forever. |
| point | An exact location in space. |
| polygon | A closed figure formed by three or more line segments that intersect only at their endpoints. |
| ray | A part of a line that starts at one endpoint and extends forever in one direction. |
| rectangle | A parallelogram with four right angles. |
| reflection | A transformation of a figure that flips the figure across a line. |
| regular polygon | A polygon with congruent sides and angles. |
| regular tessellation | A regular polygon is repeated to fill a plane. |
| rhombus | A parallelogram with all sides congruent. |
| right angle | An angle that measures 90 degrees. |
| right triangle | A triangle containing a right angle. |
| rotation | A transformation in which a figure is turned around a point. |
| rotational symmetry | A figure can be rotated less than 360 degrees around a central point and coincide with the original figure. |
| scalene triangle | A triangle with no congruent sides. |
| segment | A part of a line between two endpoints. |
| square | A rectangle with four congruent sides. |
| supplementary angles | Two angles whose measures have a sum of 180 degrees. |
| tesselation | A repeating pattern of plane figures that completely cover a plane with no gaps or overlaps. |
| transformation | A change in the size or position of a figure. |
| translation | A movement of a figure along a straight line. |
| transversal | A line that intersects two or more lines. |
| trapezoid | A quadrilateral with exactly one pair of parallel sides. |
| Triangle Sum Theorem | The theorem that states that the measures of the angles in a trianlge add up to 180 degrees. |
| vertical angles | A pair of opposite congruent angles formed by intersecting lines. |
| corresponding angles | Angles formed by a transversal cutting through 2 or more lines that are in the same relative position. |
| quadrilateral | A four sided figure |
| pentagon | A five sided figure |
| hexagon | A six sided figure |
| heptagon | A seven sided figure |
| octagon | An eight sided figure |
Combine with other sets
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