The Complete Aristotle (eng.)

completely
expressible in a formula some are separable and some are separable
and some are not.
    But clearly matter also is substance; for in all the opposite
changes that occur there is something which underlies the changes,
e.g. in respect of place that which is now here and again
elsewhere, and in respect of increase that which is now of one size
and again less or greater, and in respect of alteration that which
is now healthy and again diseased; and similarly in respect of
substance there is something that is now being generated and again
being destroyed, and now underlies the process as a ‘this’ and
again underlies it in respect of a privation of positive character.
And in this change the others are involved. But in either one or
two of the others this is not involved; for it is not necessary if
a thing has matter for change of place that it should also have
matter for generation and destruction.
    The difference between becoming in the full sense and becoming
in a qualified sense has been stated in our physical works.
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2
    Since the substance which exists as underlying and as matter is
generally recognized, and this that which exists potentially, it
remains for us to say what is the substance, in the sense of
actuality, of sensible things. Democritus seems to think there are
three kinds of difference between things; the underlying body, the
matter, is one and the same, but they differ either in rhythm, i.e.
shape, or in turning, i.e. position, or in inter-contact, i.e.
order. But evidently there are many differences; for instance, some
things are characterized by the mode of composition of their
matter, e.g. the things formed by blending, such as honey-water;
and others by being bound together, e.g. bundle; and others by
being glued together, e.g. a book; and others by being nailed
together, e.g. a casket; and others in more than one of these ways;
and others by position, e.g. threshold and lintel (for these differ
by being placed in a certain way); and others by time, e.g. dinner
and breakfast; and others by place, e.g. the winds; and others by
the affections proper to sensible things, e.g. hardness and
softness, density and rarity, dryness and wetness; and some things
by some of these qualities, others by them all, and in general some
by excess and some by defect. Clearly, then, the word ‘is’ has just
as many meanings; a thing is a threshold because it lies in such
and such a position, and its being means its lying in that
position, while being ice means having been solidified in such and
such a way. And the being of some things will be defined by all
these qualities, because some parts of them are mixed, others are
blended, others are bound together, others are solidified, and
others use the other differentiae; e.g. the hand or the foot
requires such complex definition. We must grasp, then, the kinds of
differentiae (for these will be the principles of the being of
things), e.g. the things characterized by the more and the less, or
by the dense and the rare, and by other such qualities; for all
these are forms of excess and defect. And anything that is
characterized by shape or by smoothness and roughness is
characterized by the straight and the curved. And for other things
their being will mean their being mixed, and their not being will
mean the opposite.
    It is clear, then, from these facts that, since its substance is
the cause of each thing’s being, we must seek in these differentiae
what is the cause of the being of each of these things. Now none of
these differentiae is substance, even when coupled with matter, yet
it is what is analogous to substance in each case; and as in
substances that which is predicated of the matter is the actuality
itself, in all other definitions also it is what most resembles
full actuality. E.g. if we had to define a threshold, we should say
‘wood or stone in such and such a position’, and a house we should
define as ‘bricks and timbers in such and such a position’,(or a
purpose may exist as well in some cases), and if we had to define
ice we should say ‘water frozen or solidified in such and such a
way’, and harmony is ‘such and such a blending of high and low’;
and similarly in all other cases.
    Obviously, then, the actuality or the formula is different when
the matter is different; for in some cases it is the composition,
in others the mixing, and in others some other of the attributes we
have