| A | B |
|---|
| line | a straight path that goes on forever in both directions |
| ray | part of a line having only one endpoint and going on forever in the other direction |
| line segment | a part of a line that has two end points |
| endpoint | a point at the end of a ray or line segment |
| parallel lines | lines that lie in the same plane and do not intersect (always the same distance apart) |
| intersecting lines | lines that cross at a point |
| perpendicular lines | two lines that form right angles where they intersect |
| point of intersection | the point where two lines cross, or intersect, each other |
| vertex | the point that two rays of an angle have in common |
| angle | two rays having the same endpoint |
| point | an exact position often marked by a dot |
| protractor | an instrument used to measure the size of an angle |
| degree | the unit of measure used when measuring angles |
| acute angle | an angle that measures less than 90 degrees |
| right angle | an angle that measures exactly 90 degrees |
| obtuse angle | an angle that measures greater than 90 degrees and less that 180 degrees |
| straight angle | an angle that measures exactly 180 degrees |
