 One of my more favorite terms in the field is an antecedent stimulus class. An antecedent stimulus class is a set of stimuli that share a common relationship. Stimuli in an antecedent stimulus class all evoke the same response, operant or otherwise, but they are not the same stimuli. An example of an antecedent stimulus class would be different types of phones. This phone doesn't look anything like this phone as you can see it's much larger and more efficient. But both of them are phones, kind of. This phone breaks. So now I have one phone and I have another phone. So we have two phones. Both of them are drastically different stimuli. Antecedent stimulus class, though, indicates that we will say the same thing in response to the presentation of these stimuli. Phone? Phone. That's simple. And for all of you smartasses out there that know that this isn't a phone, bugger off! I was trying to give an example.