argument/parameter?

Ok, so what is the difference between the terms "argument" and "parameter." I know one is the actual variable passed in a function call and the other is the variable that the function is looking for as in the declaration, but which is which? I knew this at one time, but it has slipped my brain.
Thanks

Argument: A variable/value that is being sent to the function.

Parameter: A variable with a namespace of the actual function that gets that argument's value.

Thank you very much.