The actualization of something in potency insofar as it is in potency.  Motion (or kinésis) is the process by which a subject passes from a given state of privation toward a given terminus or end in which that subject will have the new form in question.  Classically, motions can be of various kinds: local motion regarding place; quantitative increase; and qualitative alteration.  More broadly speaking, one can speak of motion toward the gain or loss of a substantial form as a kind of motion toward corruption or generation, although corruption and generation themselves are not motions.