DIFFERENTIA
differentia
(noun) distinguishing characteristics (especially in different species of a genus)
Source: WordNet® 3.1
Etymology
Noun
differentia (plural differentiae)
(semantics, logic, taxonomy) A distinguishing feature which marks a species off from other members of the same genus.
Source: Wiktionary
Dif`fer*en"ti*a, n.; pl. Differentiæ. Etym: [L. See Difference.]
(Logic)
Definition: The formal or distinguishing part of the essence of a species;
the characteristic attribute of a species; specific difference.
Source: Webster’s Unabridged Dictionary 1913 Edition