An angle is the space between two lines that start at the same point.

We measure angles in degrees. The degree symbol looks like this °. We show it next to a number like this 90°.

Types of angles

Angles can be between 0° and 360° (which is a full circle) and depending on the size of the angle, they are called different things:

A right angle looks like the corner of a square or the edge of a book.

It is a perfect 90°, which is often shown by a small square drawn in between the two lines.

An acute angle is an angles that is less than 90°. This makes them smaller than a right angle.

A good way to remember this angle is to think that because it is small, it is “a cute” angle.

An obtuse angle is an angle that is bigger than 90° degrees, but doesn’t reach a straight line at 180°.

When you compare two angles, you have to think to yourself, is it smaller or bigger than 90°?

Example 1:

Look at this shape, known as a quadrilateral (a four-sided, two-dimensional shape).

Angle A is a right angle.

Which angles are acute angles?

Look carefully at the other angles and compare them to the right angle. Which angles are smaller?

• B and D are acute angles because they’re clearly smaller than a right angle.

• That means angle C is an obtuse angle because it is larger than angle A.

Example 2:

Are any of the angles below obtuse?

Compare each angle to a right angle again – which are bigger than 90°?

• A and D are obtuse since they’re clearly larger than a right angle.

• B and C are acute angles then.