If we try to modify the string stored in variable *word*, JavaScript should raise an error. Any data type under a single quote, double quote, or backtick quote is a string data type.
```js
word[0] = 'Y'
word[0] = 'J'
```
This expression does not change the string stored in the variable *word*. So, we can say that strings are not modifiable or in other words immutable.