---
page_title: Functions - Configuration Language
description: >-
  An introduction to the built-in functions that you can use to transform and
  combine values in expressions.
---

# Built-in Functions

> **Hands-on:** Try the [Perform Dynamic Operations with Functions](/terraform/tutorials/configuration-language/functions?utm_source=WEBSITE&utm_medium=WEB_IO&utm_offer=ARTICLE_PAGE&utm_content=DOCS) tutorial.

The Terraform language includes a number of built-in functions that you can
call from within expressions to transform and combine values. The general
syntax for function calls is a function name followed by comma-separated
arguments in parentheses:

```hcl
max(5, 12, 9)
```

For more details on syntax, see
[_Function Calls_](/terraform/language/expressions/function-calls)
in the Expressions section.

The Terraform language does not support user-defined functions, and so only
the functions built in to the language are available for use. The documentation includes a page for all of the available built-in functions.

You can experiment with the behavior of Terraform's built-in functions from
the Terraform expression console, by running
[the `terraform console` command](/terraform/cli/commands/console):

```
> max(5, 12, 9)
12
```

The examples in the documentation for each function use console output to
illustrate the result of calling the function with different parameters.