# Function

A function is an operation or a series of operations that can be defined just once but used (or 'called') as many times as you like.

Use the Function part to start a function and the Return part to finish it.

You can change the name of the function by clicking on the name on the front of the Function part. This name must be unique and cannot be used by another function in the document.

Two types of function are available:

- Built-in functions that are ready to be called within expressions.
- Custom functions that you can create using flowchart parts and then call from expressions.

## See also:

- Function parameters
- Function return values
- Return
- Using flowcharts parts