Khan Academy

1. Protractor

1.1. The vertex of the angle goes on the center point of the protractor

1.2. Each "ticky" mark on the protractor is exactly one degree

1.2.1. In deeper math, each degree is known as a radian

2. Angle

2.1. When 2 rays share a common vertex

3. Acute Angle

3.1. An angle that's greater than 90 degrees

4. Obtuse Angle

4.1. An angle that's greater than 90 degrees

5. Right Angle

5.1. An angle that's exactly 90 degrees

6. The more degrees, the more open the angle is

6.1. Some are more open/closed than others