Full Idea
Aristotle gives us four explanations (or causes) of things: the essence (to ti estin, to ti en einai) and the form (he morphe, to eidos); the matter (hule); the source of change and generation (to kinoun); and the end (telos) at which change is directed.
Gist of Idea
Four Explanations: the essence and form; the matter; the source; and the end
Source
report of Aristotle (Physics [c.337 BCE]) by Vassilis Politis - Aristotle and the Metaphysics 2.4
Book Reference
Politis,Vasilis: 'Aristotle and the Metaphysics' [Routledge 2004], p.51
A Reaction
Politis presents these as primarily the Four Explanations, rather than under the better-known label of the 'Four Causes'. It is interesting that essence and form are lumped in together, under what is normally labelled the 'formal cause'.