> For the complete documentation index, see [llms.txt](https://guide.cronuszen.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://guide.cronuszen.com/gpcscripting/gpc-script-guide/gpc-developer-guide/definitions.md).

# Definitions

The sole purpose of a definition is to assign a value to a word and therefore make a script easier for a human to read. They do not use any bytecode space in a script. When a script is compiled the words are changed to their assigned value.

### Syntax

```
define <n> = <value or expression>;
```

| Parameter               | Description                                      |
| ----------------------- | ------------------------------------------------ |
| `<n>`                   | The name of the constant                         |
| `<value or expression>` | The value or expression assigned to the constant |

The value of the definition must be possible to compute during compilation, meaning you can use math but not math functions.

Once a word is defined and given a value, that word can be used anywhere in the script where a value is valid, as shown below:

```gpc
define my_value = 50;

main {
    if(get_val(XB1_LT)) {
        set_val(XB1_RT, my_value);
    }
}
```

If you wish to assign a value to a word and change its value during run time, you would use a [variable](/gpcscripting/gpc-script-guide/gpc-developer-guide/variables.md) instead of a `define`.


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