GNU Collaborative International Dictionary of English

Found one definition

1.       
   differentia (?), n.; pl. Differentiæ (#). [L. See Difference.]
   1. (Logic) The formal or distinguishing part of the essence of a species, by which it is distinguished from other members of its genus; the characteristic attribute of a species; specific difference; as, “a proper definition must have both genus and differentia”.
   
   [1913 Webster +PJC]
   
   
   2. the set of characteristics distinguishing an entity from related entities.
   
   [PJC]