Since in the first sense of matter or the material a thing is characterized by indetermination, we can consider it in two ways: either according to the indetermination as such, or according to the one determination that it happens to have now. In the first sense, we consider a two by four in relation to everything that it could make or become; in the second, we consider it as a wooden thing that happens to have a certain shape.
Matter can either be determined by only one form, or by many successively. As far as we know, there exists no matter which can only be one thing, which would require that the thing be eternal, for it could never break into a new shape, rot, be scattered, or be made into something else. The ancients belived- on good evidence- that the stars and planets were made of a matter that was determined to one thing, but that hypothesis was disproven.
Matter, then, while it may happen to be this thing, never looses its nature as a principle of becoming something else. When we consider something as material, we precind from considering it as a determinite thing- with a determinite shape, position, color, texture, even existence. Matter is a certain infinity; it can be this or that or some other thing. Matter, as such, is not fixed to any one particular.