Virus Definitions?

I notice that the Total Definitions of Comodo Internet Security with the Database Version 23115 was 42706069. That’s quite a large number. But I’d like to know that is this “Virus Definitions” the same with “Virus Signatures”? Or are they different and what’s the difference(s)? :-
So can anyone tell me what is “Virus Definitions” and what is “Virus Signatures”?

The Total Definitions can be found here: