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# Predefined Timing Functions

Constants that specify system-provided timing functions, used by [`init(name:)`](/documentation/QuartzCore/CAMediaTimingFunction/init(name:)).

## Topics

### Constants

[`linear`](/documentation/QuartzCore/CAMediaTimingFunctionName/linear)

Linear pacing, which causes an animation to occur evenly over its duration.

[`easeIn`](/documentation/QuartzCore/CAMediaTimingFunctionName/easeIn)

Ease-in pacing, which causes an animation to begin slowly and then speed up as it progresses.

[`easeOut`](/documentation/QuartzCore/CAMediaTimingFunctionName/easeOut)

Ease-out pacing, which causes an animation to begin quickly and then slow as it progresses.

[`easeInEaseOut`](/documentation/QuartzCore/CAMediaTimingFunctionName/easeInEaseOut)

Ease-in-ease-out pacing, which causes an animation to begin slowly, accelerate through the middle of its duration, and then slow again before completing.

[`default`](/documentation/QuartzCore/CAMediaTimingFunctionName/default)

The system default timing function. Use this function to ensure that the timing of your animations matches that of most system animations.


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