> For the complete documentation index, see [llms.txt](https://docs.langstack.com/welcome/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.langstack.com/welcome/get-started/learn-langstack/basics-and-essentials/what-is-a-variable/naming-rules-of-a-variable.md).

# Naming rules of a Variable

Users can create variables and must give them names to identify them while working in Actions. The naming rules for a variable are: 

* The variable's name must begin with a letter (A-Z or a-z). Digits (0-9) and \_ (underscore) are allowed after the first letter.
* The name cannot contain whitespaces or special characters such as !, #, %, . (dot), etc. 
* The variable name must be unique in the same scope. 
* Names are case insensitive, so the variables “mycustomer” and “MyCustomer” are identical. 
* Reserved words cannot be used as names for variables (see the list below). 
* The Langstack application reserved keywords for variables are as follows:

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