# isNegative() Function & Examples

Use the isNegative() utils function in Calcul.io. Review its syntax, edit working examples, understand the result, and explore related math functions.

## isNegative

#### isNegative(x)

Try it yourself:

```calculio
isNegative(2)
isNegative(0)
isNegative(-4)
isNegative([3, 0.5, -2])
```

---

## isNegative(): test whether a number is below zero

**isNegative(x)** returns true when x is less than zero. It makes sign-sensitive formulas and validation rules easy to read.

## Typical uses

Reject negative lengths, determine direction, or branch on a financial loss. `isNegative(-3)` is true; zero is neither negative nor positive.

## Related checks

Use [isPositive()](https://calcul.io/function/isPositive/index.md) for values above zero and [isZero()](https://calcul.io/function/isZero/index.md) for the remaining case. [sign()](https://calcul.io/function/sign/index.md) returns the sign itself, while [abs()](https://calcul.io/function/abs/index.md) removes it. Check [isNumeric()](https://calcul.io/function/isNumeric/index.md) first for untrusted input.

## Boundary care

Very small floating-point values can be negative because of rounding. Use a tolerance when the real-world rule is “effectively zero”.

[All functions](https://calcul.io/functions/index.md)