| A | B |
|---|
| acute angle | an angle with a measure between 0 and 90 degrees |
| right angle | an angle with a measure of exactly 90 degrees |
| obtuse angle | an angle with a measure between 90 degrees and 180 degrees |
| congruent | equal in size or measure |
| acute triangle | a triangle with all acute angles |
| obtuse triangle | a triangle with one obtuse angle |
| right triangle | a triangle with one right angle |
| scalene triangle | a triangle with no congruent sides |
| isosceles triangle | a triangle with at least two congruent sides |
| equilateral triangle | a triangle with all three sides congruent |
| equiangular triangle | a triangle with all three angles congruent |
| complementary angles | two angles that add up to 90 degrees |
| supplementary angles | two angles that add up to 180 degrees |
| adjacent angles | two angles next to each other that share a common ray |
| vertical angles | opposite angles formed by intersecting lines |
| perpendicular | meeting to form right angles |
| parallel lines | lines on the same plane that never intersect |
| skew lines | lines on different planes that never intersect |
| alternate interior angles | angles on opposite sides of a transversal, inside parallel lines |
| corresponding angles | angles in same relative position formed by a transversal and parallel lines |
| point | a location in space |
| line | a collection of points determined by two points, extending infinitely in opposite directions |
| line segment | part of a line bounded by endpoints |
| ray | a half line, bounded on one end and extending infinitely on the other |
| angle | two rays with a common endpoint |
| vertex | the shared endpoint of the rays of an angle |
| collinear | on the same line |
| non-collinear | not on the same line |
| straight angle | an angle with a measure of exactly 180 degrees |
| reflex angle | an angle with a measure between 180 degrees and 360 degrees |
| protractor | a tool for measuring angles |
| polygon | a flat, closed figure made up of line segments |
| concave polygon | a polygon with at least one diagonal outside the figure |
| convex polygon | a polygon with all diagonals inside the figure |
| diagonal | a line segment connecting non-adjacent vertices of a polygon |
| plane | a collection of points, determined by three non-collinear points, that extends infinitely in all directions |
| triangle | a three-sided polygon |
| transversal | a line or segment that intersects parallel lines |
| quadrilateral (or quadrangle) | a four-sided polygon |
| kite | a quadrilateral with two pairs of adjacent, congruent sides |
| trapezoid | a quadrilateral with only one pair of parallel sides |
| isosceles trapezoid | a trapezoid with non-parallel sides congruent |
| right trapezoid | a trapeziod with two right angles |
| parallelogram | a quadrilateral with two pairs of opposite, congruent sides |
| rectangle | a parallelogram with all right angles |
| rhombus | a parallelogram with all sides congruent |
| square | a parallelogram with congruent sides and all right angles |
| regular polygon | a polygon with all sides congruent and all angles congruent |
| midpoint | the center point of a segment that divides it into two congruent parts |
| translation | a "slide" rigid body movement |
| rotation | a "turn" rigid body movement |
| reflection | a "flip" rigid body movement |
