| A | B |
|---|
| triangle | 3 sided polygon |
| quadrilateral | 4 sided polygon |
| pentagon | 5 sided polygon |
| hexagon | 6 sided polygon |
| heptagon | 7 sided polygon |
| octagon | 8 sided polygon |
| nonagon | 9 sided polygon |
| decagon | 10 sided polygon |
| point | position in space |
| line | continuous straight set of points; extends infinitely in both directions |
| segment | part of a line that has two endpoints |
| plane | flat surface that extends infinitely in all directions |
| ray | part of a line that has one endpoint and continues infinitely in one direction |
| angle | formed by two rays with a common endpoint |
| right angle | measures 90 degrees |
| acute angle | measures less than 90 degrees |
| obtuse angle | measures greater than 90 degrees and less than 180 degrees |
| straight angle | measures 180 degrees |
| intersecting lines | two lines that cross at a point |
| perpendicular lines | two lines that intersect to form right angles |
| parallel lines | lines in the same plane that do not intersect |
| right triangle | a triangle containing one right angle |
| obtuse triangle | a triangle containing one obtuse angle |
| acute triangle | a triangle containing three acute angles |
| scalene triangle | a triangle with no congruent sides |
| isosceles triangle | a triangle with at least two congruent sides |
| equilateral triangle | a triangle with three congruent sides |
| congruent | having the same size, measure, and shape |
| regular polygon | a polygon in which all the sides and all the angles are congruent |
| trapezoid | a quadrilateral with exactly one pair of parallel sides |
| parallelogram | a quadrilateral with opposite sides parallel |
| rectangle | a parallelogram with 4 right angles |
| rhombus | a parallelogram with 4 congruent sides |
| square | a parallelogram with 4 right angles and 4 congruent sides |
| reflection | mirror-image of a figure |
| translation | the slide image of a figure |
| rotation | the image of a figure made by turning it |
