1.   lines that intersect at 90 degrees
2.    lines that never cross ( like train tracks)
3.    an angle that is exactly between 90 and 180 degrees
4.    an angle that is exactly 90 degrees
5.    an angle that is exactly 180 degrees
6.    an angle that is between 0 and 90 degrees
7.    acute
8.    obtuse
9.    acute
10.    right
11.    acute
12.    obtuse
13.    acute
14.    straight
15.    corner of chalkboard
corner of room
corner of paper
corner of shirt pocket
corner of desk