| A | B |
|---|
| plane | a flat surface that goes on forever |
| polygon | any geometric figure with 3 or more sides |
| line | a set of points that goes on forever in both directions |
| line segment | part of a line;with 2 endpoints |
| ray | a set of points that has 1 endpoint and goes on forever in the opposite direction |
| angle | 2 rays that meet at 1 point form this |
| right angle | an angle that is EXACTLY 90 degrees |
| acute angle | an angle that is LESS than 90 degrees |
| obtuse angle | an angle that is MORE than 90 degrees |
| arc | a curved line segment that runs along a circle's edge |
| parallel lines | 2 or more lines, on the same plane, that will never meet |
| perpendicular lines | 2 lines that meet or cross to form a 90 degree angle |
| perimeter | the distance around a polygon |
| circumference | the distance around a circle |
| area | the number of "squares" inside a plane figure |
| diameter | a line that goes completely across a circle,through the centerpoint |
| radius | a line that goes 1/2 across a circle,from the centerpoint |
| chord | a line that crosses through a circle, but not through the centerpoint |
| parallelogram | 4-sided polygon with opposite sides that are parallel |
| square | a parallelogram with 4 equal sides and four 90 degree angles |
| rhombus | a parallelogram with 4 equal sides but NO 90 degree angles |
| rectangle | a parallelogram with opposite sides equal, and four 90 degree angles |
| trapezoid | a 4-sided polygon with only 2 parallel sides |
| pentagon | a 5-sided polygon |
| hexagon | a 6-sided polygon |
| octagon | an 8-sided polygon |
| protractor | an instrument used to measure angles |
| compass | an instrument used to draw circles |
| congruent | equal measurements |
| circle | a closed curve where the edges are an equal distance from the centerpoint |
| triangle | any 3-sided figure |
| equilateral triangle | a triangle with 3 equal sides |
| isosceles triangle | a triangle with 2 equal sides |
| scalene triangle | a triangle with NO equal sides |
| right triangle | a triangle with one 90 degree angle |
| acute triangle | a triangle with 3 acute angles |
| obtuse triangle | a triangle with 1 obtuse angle |
