| Term | Definition |
| point | an exact location in space |
| line | an endless collection of points along a straight path |
| line segment | part of a line that has two end points |
| ray | part of a line that has one endpoint and extends endlessly in the other direction |
| plane | an endless flat surface that is named by any three parts not in the same line |
| intersecting lines | lines that have exactly one point in common |
| parallel lines | lines in the same plane that never intersect |
| perpendicular lines | two lines that intersect at right angles |
| acute angle | an angle that measure less than 90 degrees |
| right angle | an angle that measures 90 degrees |
| obtuse angle | an angle with a measure greater than 90 degrees but less than 180 degrees |
| straight angle | an angle that measures 180 degrees |
| polygon | a closed plane figure with 3 or more sides |
| quadrilateral | a 4 sided polygon |
| pentagon | a 5 sided polygon |
| hexagon | a 6 sided polygon |
| heptagon | a 7 sided polygon |
| octagon | a 8 sided polygon |
| nonagon | a 9 sided polygon |
| decagon | a 10 sided polygon |
| acute triangle | a triangle with 3 acute angles |
| obtuse triangle | a triangle with one obtuse angle |
| equilateral triangle | a triangle with all sides equal |
| isosceles triangle | a triangle with two congruent sides |
| scalene triangle | a triangle that has no congruent sides |
| parallelogram | parallelogram- a quadrilateral with 2 sets of parallel sides |
| rhombus | a parallelogram with 4 equal sides |
| square | a rhombus with 4 right angles |
| rectangle | a parallelogram with 4 right angles |
| trapezoid | a quadrilateral with only 1 set of parallel sides |
| vertex | where edges meet |
| edge | where faces meet on a space figure |
| face | a flat surface on a space figure |
| right triangle | a triangle with one right angle |