---
title: domain
framework: phase
role: symbol
role_heading: Instance Property
path: phase/phaseenvelope/domain
---

# domain

The range of the envelope’s possible input values.

## Declaration

```swift
var domain: PHASENumericPair { get }
```

## Discussion

Discussion This property is an ordered pair that describes input values along the x axis for which the evaluate(x:) function can produce a non-zero output. The first number in the pair is the minimum input value, and the second number in the pair is the maximum input value. When an envelope graphs volume over time, the framework scales the domain by unitsPerSecond.  Likewise, when an envelope graphs volume over distance, the framework scales this property by unitsPerMeter.

## See Also

### Bounding the Input

- [range](phase/phaseenvelope/range.md)