## PI

The `PI` function in ES|QL returns the mathematical constant Pi, which is the ratio of a circle's circumference to its diameter.

### Examples

Here are a couple of examples of how you can use the `PI` function in ES|QL queries:

```esql
ROW PI()
```

In this example, the `PI` function is used to simply return the value of Pi.

```esql
FROM employees
| EVAL circle_area = PI() * POW(radius, 2)
```

In this second example, the `PI` function is used in a calculation to determine the area of a circle, given the radius stored in the `radius` field of the `employees` index.