A function that is a member of a class will be referred to as a method or as a member function. A function that is not part of a class may be described as a non-member function. The generic term function applies to functions that are either member functions or non-member functions.

That which is passed to a function is referred to as an argument or as a parameter. When defining a function, the identifiers associated with the parameters are referred to as formal parameters or as formal arguments. To distinguish between the formal parameters and the values passed to a function upon calling the function, the term actual may precede the term parameter or argument. Parameters passed to operators are often referred to as operands.