# Types of Angles (Mathematics Lesson)

# Types of Angles

There are different types of angle.

Angles can be:

# Acute Angles

An acute angle is an angle of less than 90°.

# Right Angles

A right angle is an angle of 90°.

**Don't forget:** Right angles are often denoted by adding a small right angle that forms a square with the angle.

# Obtuse Angles

An obtuse angle is an angle greater than 90° and less than 180°.

# Straight Angles

A straight angle is an angle of 180°.

Read more about straight angles

# Reflex Angles

A reflex angle is an angle greater then 180° and less than 360°.

# Full Angles

A full angle is an angle of 360°.

##### Curriculum

##### Interactive Test

**show**

Here's a second test on the types of angle.

Here's a third test on the types of angle.

##### Note

# What Is an Angle?

An angle is created by two rays that have a common end point, called the vertex.

# Who Classified Angles?

Euclid classified angles in his book, *Elements*.

**Definition 10:** "When a straight line standing on a straight line makes the adjacent angles equal to one another, each of the equal angles is right".

**Definition 11:** "An obtuse angle is an angle greater than a right angle".

**Definition 12:** "An acute angle is an angle less than a right angle".

# Oblique Angles

Acute and obtuse angles are also oblique angles. Oblique angles are neither right angles nor multiples of right angles.