Answer:
2. either of two angles whose sum is 180°.
3. each of the pairs of opposite angles made by two intersecting lines.
4. Two angles are adjacent when they have a common side and a common vertex (corner point) and don't overlap.
5. The acute angle is an angle less than 90°
6. It is more than 90° and less than 180°.
7. an angle of 90°
8. an angle of 180°