cadl/docs/language-basics/alias.md

id	title
aliases	Aliases

Aliases

Aliases are a convenient way to define shorthand for types, especially when dealing with complex expressions. They simplify the syntax but don't have a representation in the type graph. As a result, you can't decorate aliases. If you need to give an alternate name to a model, use model is.

You can define an alias using the alias keyword.

alias Options = "one" | "two";