| A | B |
|---|
| two rays with the same endpoint | angle |
| the perimeter of a circle | circumference |
| a polygon that looks like it is "collapsed" or has a "dent" on one or more sides | concave polygon |
| a chord that pauses through the center of a circle | diameter |
| lines that are coplanar and hve exactly one point in common | intersecting lines |
| a polygon that you can fold in half along a line so that the two halves match exactly | line symmetry |
| the distance around a two-dimensional shape | perimeter |
| two lines or segments that form a right angle | perpendicular |
| a closed figure formed from line segments that meet only at their endpoints | polygon |
| a segment from the center of a circle to a point on a circle | radius |
| a polygon with sides that are all the same length and angles that are all the same side | regular polygon |
| an angle that measures exactly 90 degrees | right angle |
| a corner of a polygon, where two sides meet | vertex |
