An angle is formed when two straight lines meet. With any angle we measure the amount of turn, and the unit we use is called a degree. If you make a complete revolution, the turn goes through 360 degrees, written as 360°.

Half a revolution (which means you face the exact opposite way) is a turn of 180°. We can call this a straight angle.

A quarter of a revolution is a turn of 90°, which we also call a right angle.

If an angle is less than 90°, we call it an acute angle.

If an angle is more than 90°, but less than 180°, we call it an obtuse angle.

If an angle is more than 180°, we call it a reflex angle.