differentia

The character that distinguishes one species from others within the same genus is called the differentia specifica.

The Political Ideas of St. Thomas Aquinas Dino Bigongiari 1997

For we are still faced with the apparent fact that genus + differentia constitutes a plurality even if the differentia is the last, or “completing,” one.

Aristotle's Metaphysics Cohen, S. Marc 2008

Popularly this was described by saying that the differentia is the knife that carves a species out of the genus.

The Political Ideas of St. Thomas Aquinas Dino Bigongiari 1997

By quality I mean not that which is in the substance (for even the differentia is a quality), but the passive quality, in virtue of which a thing is said to be acted on or to be incapable of being acted on.

Metaphysics Aristotle 2002

Likewise you must inquire also if the species or any of the objects that come under it is predicated of the differentia: for this is impossible, seeing that the differentia is a term with a wider range than the various species.

Topics 2002

Moreover, if any of the species be predicated of it, the result will be that the differentia is a species: if, for instance, ‘man’ be predicated, the differentia is clearly the human race.

Topics 2002

And here, to prevent the notion of differentia from being restricted within too narrow limits, it is necessary to remark, that a species, even as referred to the same genus, will not always have the same differentia, but a different one, according to the principle and purpose which preside over the particular classification.

A System Of Logic, Ratiocinative And Inductive (Vol. 1 of 2) John Stuart Mill 1839

And here, to prevent the notion of differentia from being restricted within too narrow limits, it is necessary to remark, that a species, even as referred to the same genus, will not always have the same differentia, but a different one, according to the principle and purpose which preside over the particular classification.

A System Of Logic, Ratiocinative And Inductive John Stuart Mill 1839

This gives the 'differentia' of the Utilitarian considered as one species of the genus 'Radical.'

The English Utilitarians, Volume II (of 3) James Mill Leslie Stephen 1868

I read it in Latin, and it says: the substances, that is human beings or cats are a composition of real components, but the accidence for example the colour white, though can be defined with genus and differentia, has only a mental composition.

Clarification 2009