# NaN

A special Number value meaning the result is not a valid number.

## What is **NaN** in JavaScript?

**NaN** — A special Number value meaning the result is not a valid number.

```javascript
const result = Number("tea");
const invalid = Number.isNaN(result);
```

Level: Novice · [More JavaScript terms at this level](https://www.ask-codey.com/glossary/subjects/javascript/novice)

Updated: September 28, 2026

Source: https://www.ask-codey.com/glossary/nan