| A | B |
|---|
| ray | a part of a line that extends indefinitely from one point in one direction |
| vertex | a point where two lines intersect |
| angle | two rays with a common endpoint |
| decagon | a ten-sided polygon |
| degree | the most common unit of measure for angles |
| protractor | a tool used to measure angles |
| acute angle | an angle between 0 and 90 degrees |
| obtuse angle | an angle between 90 and 180 degrees |
| right angle | a 90 degree angle |
| pentagon | a five-sided polygon |
| complementary | two angles that have a sum of 90 degrees |
| supplementary | two angles that have a sum of 180 degrees |
| polygon | a simple closed figure formed by straight line segments |
| regular polygon | a figure with all angles congruent and all sides congruent |
| parallel | lines going in the same direction and always being the same distance apart (they will never cross) |
| quadrilateral | a four-sided polygon |
| square | a rectangle with all sides congruent |
| parallelogram | a quadrilateral with opposite sides congruent and parallel |
| rectangle | a parallelogram with four right angles |
| equilateral triangle | a triangle with all sides congruent |
| scalene triangle | a triangle with no sides congruent |
| hexagon | a six-sided polygon |
| isosceles triangle | a triangle with two sides congruent |
| acute triangle | a triangle with all angles between 0 and 90 degrees |
| octagon | an eight-sided polygon |
| obtuse triangle | a triangle with one angle between 90 and 180 degrees |
| right triangle | a triangle with one 90 degree angle |
| line | a straight path that goes on forever in opposite directions |
| line segment | a part of a line that includes two points called endpoints and all points between them |
| straight angle | a 180 degree angle |
| perpendicular lines | two lines that intersect at a 90 degree angle |
| triangle | a three-sided polygon |
| heptagon | a seven-sided figure |
| nonagon | a nine-sided figure |
| decagon | a ten-sided figure |
| congruent | 2 line segments or angles having the same measure |
| rhombus | a parallelogram with 4 equal sides |
| trapezoid | a quadrilateral with exactly one pair of parallel sides |
