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# UnitFrequency

A unit of measure for frequency.

```
class UnitFrequency
```

## Overview

You typically use instances of [`UnitFrequency`](/documentation/Foundation/UnitFrequency) to represent specific quantities of frequency using the [`NSMeasurement`](/documentation/Foundation/NSMeasurement) class.

### Frequency

Frequency is a quantity of occurrences for a repeating event over time. The SI unit for frequency is the hertz (Hz), which is a derived as one occurrence per second (`1 Hz = 1 / 1s`).

The [`UnitFrequency`](/documentation/Foundation/UnitFrequency) class defines its [`baseUnit()`](/documentation/Foundation/Dimension/baseUnit()) as [`hertz`](/documentation/Foundation/UnitFrequency/hertz), and provides the following units, which are initialized using [`UnitConverterLinear`](/documentation/Foundation/UnitConverterLinear) converters with the specified coefficients:

|Name      |Method                                                                          |Symbol|Coefficient|
|----------|--------------------------------------------------------------------------------|------|-----------|
|Terahertz |``doc://com.apple.foundation/documentation/Foundation/UnitFrequency/terahertz`` |THz   |`1e12`     |
|Gigahertz |``doc://com.apple.foundation/documentation/Foundation/UnitFrequency/gigahertz`` |GHz   |`1e9`      |
|Megahertz |``doc://com.apple.foundation/documentation/Foundation/UnitFrequency/megahertz`` |MHz   |`1000000.0`|
|Kilohertz |``doc://com.apple.foundation/documentation/Foundation/UnitFrequency/kilohertz`` |kHz   |`1000.0`   |
|Hertz     |``doc://com.apple.foundation/documentation/Foundation/UnitFrequency/hertz``     |Hz    |`1`        |
|Millihertz|``doc://com.apple.foundation/documentation/Foundation/UnitFrequency/millihertz``|mHz   |`0.001`    |
|Microhertz|``doc://com.apple.foundation/documentation/Foundation/UnitFrequency/microhertz``|µHz   |`0.000001` |
|Nanohertz |``doc://com.apple.foundation/documentation/Foundation/UnitFrequency/nanohertz`` |nHz   |`1e-9`     |

## Topics

### Accessing the Base Unit

[`baseUnit()`](/documentation/Foundation/Dimension/baseUnit())

Returns the base unit.

### Accessing Predefined Units

[`terahertz`](/documentation/Foundation/UnitFrequency/terahertz)

The terahertz unit of frequency.

[`gigahertz`](/documentation/Foundation/UnitFrequency/gigahertz)

The gigahertz unit of frequency.

[`megahertz`](/documentation/Foundation/UnitFrequency/megahertz)

The megahertz unit of frequency.

[`kilohertz`](/documentation/Foundation/UnitFrequency/kilohertz)

The kilohertz unit of frequency.

[`hertz`](/documentation/Foundation/UnitFrequency/hertz)

The hertz unit of frequency.

[`millihertz`](/documentation/Foundation/UnitFrequency/millihertz)

The millihertz unit of frequency.

[`microhertz`](/documentation/Foundation/UnitFrequency/microhertz)

The microhertz unit of frequency.

[`nanohertz`](/documentation/Foundation/UnitFrequency/nanohertz)

The nanohertz unit of frequency.

[`framesPerSecond`](/documentation/Foundation/UnitFrequency/framesPerSecond)

The frames per second unit of frequency.


---

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