# Definition:Angle/Types

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## Definition

Angles can be divided into categories:

### Zero Angle

The **zero angle** is an angle the measure of which is $0$ regardless of the unit of measurement.

### Acute Angle

An **acute angle** is an angle which has a measure between that of a right angle and that of a zero angle.

### Right Angle

A **right angle** is an angle that is equal to half of a straight angle.

### Obtuse Angle

An **obtuse angle** is an angle which has a measurement between those of a right angle and a straight angle.

### Straight Angle

A **straight angle** is defined to be the angle formed by the two parts of a straight line from a point on that line.

### Reflex Angle

A **reflex angle** is an angle which has a measure between that of a straight angle and that of a full angle.

### Full Angle

A **full angle** is an angle equivalent to one full rotation.

It is possible to consider angles outside the range $\closedint {0 \degrees} {360 \degrees}$, that is, $\closedint 0 {2 \pi}$.

However, in geometric contexts it is usually preferable to convert these to angles inside this range by adding or subtracting multiples of a full angle.