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# friction

The particle’s friction coefficient.

```
static let friction: SCNParticleSystem.ParticleProperty
```

## Discussion

This property’s value is a floating-point scalar (an <doc://com.apple.documentation/documentation/Foundation/NSNumber> object for particle property controllers, or a single `float` value for particle event or modifier blocks).

The particle system’s [`particleFriction`](/documentation/SceneKit/SCNParticleSystem/particleFriction) and [`particleFrictionVariation`](/documentation/SceneKit/SCNParticleSystem/particleFrictionVariation) properties determine the initial friction coefficient for each particle.

---

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