1. Act and Potency
As the most basic explanation for the relation of being and non-being and thus meaning of change
Act or Actuality
Refers to the being or the act of existence of something and while always related to potency is prior and superior to potency. A real being that exists is an actual being. A real being that can exist but does not is a potent being. In so far that anything exists, it is actual;hence actuality is perfection.
Potency or Potentiality
Refers to the potent act or being of something. A real being can exist but does not, is potential being. Insofar as anything that existable does not exist, it is potential; hence, potentiality is imperfection; it is unfufillement. This is why St.Thomas Aquinas defines God, the infinite being, is pure act in whom there is no potentiality.
Change or motion or becoming
Refers to the "actualization of potency"
The transit from potentiality to actuality is called becoming or motion or change. All finite being changes God who is Pure Actuality does not change.
the principle of in a thing's being by which it is able to be determined by form, potency, as vs. actuality
Substance and Accidents
As a further refinement in the explanation of change and the constitution of a being. There are ten categories of being. The first one is substance and the others are the nine type of accident" quantity, quality, relation, action, passion/passivity. place, time, posture, habit.
A being that exists in itself rather than in another. A man is a substance, a dog is a substance, an apple is a substance, an automobile is an artificial union of a number of substances
That mod of being which can only exist in another being, as a modification or attribute of a substance. Thus, the size of a man is an accident or accidental; the color of an apple is an accident.
An agent which by its acting produces existence of change in another (man who carves the statue, his tool is called the instrumental cause)
Being, one, true, good - each is "controvertible" with being in the sense that each designates one and the same thing - namely, being - under a different aspect( the Transcendentals differ in sense but not in reference).