Simple question, but I often hear these three terms defined with such ferocity, but which have been known to me to mean different things over the years.

What are the "correct" definitions of "Procedures", "Methods", "Function", "Subroutines", etc?

I'm going with a different answer here: practically speaking, there's really no difference, with the slight exception that "method" usually refers to a subroutine associated with an object in OO languages.

The terms "procedure, function, subroutine, subprogram, and method" all really mean the same thing: a callable sub-program within a larger program.  But it's difficult to come up with a definition that captures all variant usages of these terms, because they are not used consistently across programming languages or paradigms.

You might say a function returns a value.  Well, the following C function doesn't return a value:

void f() { return; }


...but I doubt you'd find anyone who would call it a procedure.  

Sure, in Pascal, procedures don't return values and functions return values, but that's merely a reflection of how Pascal was designed.  In Fortran, a function returns a value, and a subroutine returns multiple values.  Yet none of this really allows us to come up with a "universal" definition for these terms.

In fact, the term "procedural programming" refers to a whole class of languages, including C, Fortran and Pascal, only one of which actually uses the term "procedure" to mean anything.

So none of this is really consistent.  The only exception is probably "method", which seems to be used almost entirely with OO languages, referring to a function that is associated with an object.  Although, even this is not always consistent.  C++, for example, usually uses the term "member function" rather than method, (even though the term "method" has crept into the C++ vernacular among programmers.)

The point is, none of this is really consistent.  It simply reflects the terminology employed by whatever languages are en vogue at the time.
