differentia

plural differentiae

1. biologyA distinguishing feature which marks a species off from other members of the same genus.

   In the case of a word like “surfboard,” the differentiae seem pretty clear. How is this board different from all other boards?

   2017, Kory Stamper, Word By Word, Vintage, published 2018, page 116

   2 more examples

   That character, it seems to me, should be regarded as the practically important differentia of religion for our purpose; and just what it is can easily be brought out by comparing the mind of an abstractly conceived Christian with that of a moralist similarly conceived.

   1902, William James, “Lecture II: Circumscription of the Topic”, in The Varieties of Religious Experience: A Study in Human Nature […] , New York, N.Y.; London: Longmans, Green, and Co. […], →OCLC, page 45

   If genera are different and co-ordinate, their differentiae are themselves different in kind. Take as an instance the genus ‘animal’ and the genus ‘knowledge’. ‘With feet’, ‘two-footed’, ‘winged’, ‘aquatic’, are differentiae of ‘animal’; the species of knowledge are not distinguished by the same differentiae.

   1928, E. M. Edghill, Categories, translation of original by Aristotle