To describe this concept I've always used a boat as the subject.
Imagine you have a boat. Now take a piece off of it. Is it still a boat? How far can you go until it no longer holds the distinction of being a boat?
Imagine you have a boat. Now take a piece off of it. Is it still a boat? How far can you go until it no longer holds the distinction of being a boat?
Yes, I know that submarines are colloquially known as (and are in fact) boats.