> For the complete documentation index, see [llms.txt](https://docs.work-relay.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.work-relay.com/automations/functions-and-formulas/introduction-and-usage.md).

# Introduction and usage

The Work-Relay functions is very powerful and flexible tool that may help to build your complex logic and get rid of custom code in your application. You can use functions in the Work-Relay Processes, Forms and Actions.

The Work-Relay application provides its own library of functions, with the ability to extend the library with client custom functions.

To use the function(s) or expression in your component configuration you have to wrap the whole expression with `FORMULA[]` construction, except the places where the type of content is "Formula" (for example Action conditions).

**Example 1:**

{% code overflow="wrap" %}

```apex
1 + 2 = FORMULA[1 + 2]
```

{% endcode %}

**Example 2:**

{% code overflow="wrap" %}

```apex
The current year is "FORMULA[FORMAT({$system.Date}, 'yyyy')]"
```

{% endcode %}

User can define custom functions and register them in the system. [Read the proper article](/automations/functions-and-formulas/how-to-register-a-custom-function.md) to know more.