What is dust?
What do you mean by 'dust'?
Well, by dust, we're talking about small particles, because remember that when things form to start with, they don't necessarily have to form big things and then be ground down into little things. Small things will attract other small things because they'll stick together, one way or another. So when we're talking about dust, we're talking about amorphous materials that can include big bits, small bits, and bits of gas. So it's a way of not having to define exactly what that entity is, but saying it's a mixture of chemical entities which have all of the necessary pre-requisite ingredients to actually form planets and stars.