| A | B |
|---|
| intersect | 2 lines cross |
| point of intersection | where the lines cross |
| parallel lines | if 2 lines in the same plane do not intersect |
| perpendicular | when two lines make square corners at the point of intersection |
| right angle | angle made by perpendicular lines |
| straight angle | formed by two right angles |
| acute angle | angle smaller than a right angle |
| obtuse angle | an angle larger than a right angle but small than a straight angle |
| polygon | more than one angle |
| side | each segment of a polygon |
| vertex | each endpoint of a side of the polygon |
| vertices | plural of vertex |
| triangle | polygon with fewest number of sides (3) |
| quadrilateral | polygon with 4 sides |
| pentagon | polygon with 5 sides |
| hexagon | 6 |
| heptagon | 7 |
| octagon | 9 |
| nonagon | 9 |
| decagon | 10 |
| undecagon | 10 |
| dodecagon | 12 |
| concave polygon | polygon with an indectation (cave) |
| convex polygon | polygon without indentation (no cave) |
| equilateral polygon | polygon with equal sides |
| equiangular polygon | all angles have same measures |
| regular polygon | polygons with all sides the same length and all angles have same measures |
| tick marks | marks to denote sides whose lengths are equal and angles whose measures are equal |
| triangle | 3 sides and 3 angles, sum of measures in 180 degrees |
| right triangle | if triangle has a right angle |
| acute triangle | if all angles have measures less than 90 degrees |
| obtuse triangle | if one angle has measures more than 90 degrees |
| equilateral triangle | all angles are equal |
| isosceles triangle | triangle that has at least 2 sides of equal length |
| equilateral triangle | triangle with lengths of all sides equal |
| scalene triangle | all sides of a triangle that have different lengths |
| parallelagram | quadrilateral with 2 parallel sides |
| trapezoid | quarilateral with exactly 2 parallel sides |
| rectangle | parallelogram with 4 right angles |
| rhombus | equilateral parallelogram |
| square | a rhombus with 4 right angles |
