Projectionist

In everyday usage, “parameter” and “argument” are used interchangeably to refer to the things that you use to define and call methods or functions.
Often this interchangeability doesn’t cause ambiguity. It should be noted, though, that conventionally, they refer to different things.
A “parameter” is the thing used to define a method or function while an “argument” is the thing you use to call a method or function.
Parameter:
def foo(param) ... end
Argument:
foo(arg) # => obj

Ultimately, it doesn’t really matter what you say. People will understand from the context.