Full Idea
With respect to scientific usage, we can say that the real essence of a thing will consist very largely of powers or, in modern terms, dispositional properties.
Gist of Idea
The real essence of a thing is its powers, or 'dispositional properties'
Source
Irving M. Copi (Essence and Accident [1954], p.718)
Book Reference
-: 'Journal of Philosophy' [-], p.718
A Reaction
Once again, Copi is a hero. I personally love the word 'powers' in metaphysics (and dislike the word 'properties', which is lost in a fog of confusion). See Molnar on 'powers' and Mumford on 'dispositions'.