Aristotle/Poetics/2.1447a8-1448b3

Mimêsis is differentiated according to "in which" ("in what", heterois mimeisthai), "what" ("on what", hetera), and "how" (heterós), being translated variously as the means employed (matter, medium), the objects 'mimetised' (subject) and the manner in which the mimêsis is effected (mode, method).