Full Idea
Matter, in the proper sense of the term, is to be identified with the substratum which is receptive of coming-to-be and passing-away; but the substratum of the remaining kinds of change is also matter, because these substrata receive contraries.
Clarification
The substratum [to hupokeimenon] is 'that which lies under' a thing
Gist of Idea
Matter is the substratum, which supports both coming-to-be and alteration
Source
Aristotle (Coming-to-be and Passing-away (Gen/Corr) [c.335 BCE], 320a03)
Book Reference
Aristotle: 'The Basic Works of Aristotle', ed/tr. McKeon,Richard [Modern Library Classics 2001], p.485
A Reaction
This must be compared with his complex discussion of the role of matter in his Metaphysics, where he has introduced 'form' as the essence of things. I don't think the two texts are inconsistent, but it's tricky... See Idea 12133 on types of change.
Related Idea
Idea 12133 If the substratum persists, it is 'alteration'; if it doesn't, it is 'coming-to-be' or 'passing-away' [Aristotle]