Full Idea
Plato and Aristotle have a shared general conception of essence: the essence of a thing is what that thing is simply in virtue of itself and in virtue of being the very thing it is. It answers the question 'What is this very thing?'
Gist of Idea
Plato and Aristotle take essence to make a thing what it is
Source
report of Plato (works [c.375 BCE]) by Vassilis Politis - Aristotle and the Metaphysics 1.4
Book Reference
Politis,Vasilis: 'Aristotle and the Metaphysics' [Routledge 2004], p.16