GLOSSARY
angle - a figure formed by two rays with a common endpoint
| acute angle | angle measuring more than 0 degrees but less than 90 degrees |
| obtuse angle | angle measuring more than 90 degrees but less than 180 degrees |
| straight angle | angle measuring exactly 180 degrees |
| right angle | angle measuring exactly 90 degrees |
intersecting lines - lines with one point in common
line - a collection of points along a straight path extending endlessly in both directions
line segment - a part of a line between two endpoints
parallel lines - lines in the same plane that do not intersect
parallelogram - a quadrilateral with two pairs of parallel sides
perpendicular lines - lines that intersect to form right angles
plane - a flat surface extending endlessly in all directions
point - marks an exact location in space
protractor - an instrument used to measure angles
polygon - an enclosed figure bounded by straight lines
| triangle | three sided polygon |
| quadrilateral | four sided polygon |
| pentagon | five sided polygon |
| hexagon | six sided polygon |
| septagon | seven sided polygon |
| octagon | eight sided polygon |
| nonagon | nine sided polygon |
| decagon | ten sided polygon |
quadrilateral - a polygon with four sides
| parallelogram | quadrilateral with opposite sides parallel |
| rhombus | parallelogram with all sides equal |
| rectangle | parallelogram with four right angles |
| square | rectangle with four equal sides |
skew lines - lines that lie in different planes; they do not intersect and are not parallel
symmetry - a figure has symmetry if it can be folded along a line so that the two resulting parts match exactly
triangle - a polygon with three sides
| acute triangle | triangle with three acute angles |
| obtuse triangle | triangle with one obtuse angle |
| right triangle | triangle with one right angle |
| equilateral triangle | triangle with three equal sides |
| isosceles triangle | triangle with two equal sides |
| scalene triangle | triangle with no equal sides |