Univocal predication: application of a term to two different subjects with the same definition of being. (E.g. Socrates is an animal and Secretariat is an animal.)
Equivocal predication: application of a term to two different subjects with a different definition of being. (E.g. Chase is a bank and the sandy stretch along the left side of the river is a bank.)
Pros hen predication: application of a term to two different subjects where the definition of being is different, but where one definition is derivative and points to the other definition as primary. (E.g. Brian is healthy and broccoli is healthy. Brian’s being healthy here means that he has a good bodily condition, while broccoli’s being healthy means that broccoli is productive of a good bodily condition in a thing like Brian. This second sense of healthy points to the first, as is evident, since it refers to it in its definition.)
Category: A most general kind of being. (Aristotle says, perhaps correctly, that there are ten categories: substance, quantity, relation, quality, where, when, position, having, action, passion.)
Primary Substance: an individual in the category substance
Secondary Substance: the species and genera of an individual in the category of substance that pick out what that individual is, or by extension the species and genera of an individual in other categories that pick out what that individual is. E.g. the secondary substances of Secretariat are horse, animal, etc., while the secondary substances of this here canary yellow, i.e. the one belonging to Russell the canary, are canary yellow, yellow, color, quality.
Accident: a being in a category other than substance
Property: an accident that flows from the essence of a substance, also called a per se accident, or a necessary accident. E.g. heat is a property of fire, whereas being blue is not a property of fire, though fire is sometimes blue.
Form: that through which something has esse (existence)
Matter: that which is in potentiality to esse (existence)
Subject: an underlying thing (this term is frequently substituted for “matter” and vice versa)
Privation: the lack of a form that a thing could have. (E.g. a blind man has the privation of the power to see, which we call blindness. A rock cannot see, but it is not blind, for it could not even possibly have the power to see. Thus it does not have the privation of the power to see which we call blindness.
Essence (Essentia): “the what it is to be” something. E.g. the essence of a human being is to be a composite of body and soul. The essence of the soul is to be the first actuality or form of a body powerful for life, etc. Essence is sometimes also called the “substance of” something, as well as a thing’s quiddity or nature.
Existence (Esse/Actus Essendi): the act of existence through which an essence has existence.
