Regarding the Greek words OUSIA and MORPHE
"If we stress the classical usage of this term [MORPHE], the technical sense of Aristotelian philosophy suggests itself: MORPHE, although not equivalent to OUSIA ('being, essence'), speaks of essential or characteristic attributes and thus is to be distinguished from SCHEMA(the changeable, external fashion). In a valuable essay on MORPHE and SCHEMA, [Lightfoot] argued along these lines and remarked that even in popular usage these respective meanings could be ascertained. The many references where MORPHE is used of physical appearance . . . make it difficult to maintain Lightfoot's precise distinction, though there is an important element of truth in his treatment" (Moises Silva, Philippians, 113-114).
According to F.E. Peters (Greek Philosophical Terms), OUSIA can mean "substance, existence" (page 149). Peters has more to say about OUSIA in Aristotle, but I will just quote this brief snippet:
"OUSIA [in Plato] even approaches the Aristotelian usage as 'essence' in Phaedo 65d, 92d, and Phaedrus 245e where it is equivalent to 'definition'" (Peters, pages 149-150).
MORPHE is possibly a cognate word of the Latin term FORMA.