Full Idea
The genera and the differentiae are predicated in the category of essence.
Gist of Idea
The genera and the differentiae are part of the essence
Source
Aristotle (Topics [c.331 BCE], 153a19)
Book Reference
Aristotle: 'Posterior Analytics and Topica', ed/tr. Tredennick,H/Forster,ES [Harvard 1960], p.657
A Reaction
The definition is words, and the essence is real, so our best definition might not fully attain to the essence. Aristotle has us reaching out to the world through our definitions.