The Collaborative International Dictionary
differentia \dif`fer*en"ti*a\, n.; pl. Differenti[ae]. [L. See Difference.]
(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.
the set of characteristics distinguishing an entity from related entities.
n. (plural of differentia English)
n. distinguishing characteristics (especially in different species of a genus)
[also: differentiae (pl)]