from
The Collaborative International Dictionary of English v.0.48
differentia \dif`fer*en"ti*a\, n.; pl. {Differenti[ae]}. [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]