In ARF, global variables are defined using data sections. However, local variables are defined whenever there is a declaration. Declarations consist of a variable name, a colon, and a type specifier.
Everything follows a pattern of definition -> instantiation. Variables are defined by defining their type and initial value using a type specifier, and they are instantiated at that point in the code. Wheverever in a phrase a variable can be used, it can be defined.
It is very useful to define a variable's value based on the return value from a function call. For this purpose, return direction is used.
To define a variable normally, a let phrase is used.
Multiple variables may be defined in a single let phrase.
You can even define a variable as an argument to a function.