The first paragraph below is just in case you have any specific interest in my general answer:
It has to do with a concept called the "extension and comprehension of terms" and the requirement for both the "genus and a specific difference" for a good definitions.
So by analogy, I live in the "States." and specifically in Texas. Texas is a specific part of the United States; but you just want to know what part of the world I live in relative to Didge in Australia, then the "States" may be a sufficient "level of inference" (sorry, another general term). On the other hand, if Didge is sending me a complimentary copy of his book, he will need to know my street address and the specific city.
Similarly, if my "knee" hurts, you will have an idea of what I am talking about. On the other hand, if you want me to be more specific, I could say it hurts inside the "knee joint" of above, or below, or to either side of the leg by the knee---and that would give you a better idea of what I may be feeling and what kind of injury I might have sustained.
