Type of Angles - Description
Acute Angle - an angle that is less than 90°
Right Angle - an angle that is 90° exactly
Obtuse Angle - an angle that is greater than 90° but less than 180°
Straight Angle - an angle that is 180° exactly
Reflex Angle - an angle that is greater than 180° But less than 360 degrees
Positive angle goes counterclockwise (opposite direction that clocks go). A negative angle goes clockwise.The corner point of an angle is called the vertex and the two straight sides are called arms. The angle is the amount of turn between each arm.
There are two main ways to label angles:
1. give the angle a name, usually a lower-case letter like a or b, or sometimes a Greek letter like α (alpha) or θ (theta)
2. or by the three letters on the shape that define the angle, with the middle letter being where the angle actually is (its vertex).