Materia - the potential and determinable part of a composite, i.e., that from which something arises or of which it consists, synonym of subiectum ex quo, the opposite of forma.
Forma - the actualizing principle that makes a thing to be what it is, the opposite of materia. In the ontological order it is the formal cause, the form-giving principle, and is very much the same as essentia, natura, quod quid erat esse, quidditas, species, and substantia; in the logical order it is species, idea, exemplar, and imago. In the thought of St. Thomas, it is a concept of great variety and fecundity, and generally signifies actuality in contrast to the potentiality of matter, or determination of quality or kind in contrast to the indeterminancy of matter. It is not something pre-existing, but is conceived of as being united with primary matter to constitute the substance of a thing. Other forms, called accidental, then appear to clothe the substance with its predicamental accidents. Some forms, the angels and human souls, exist independently of matter; but most forms disappear when the composite of which they are the principle of actual existence is dissolved.
Privatio - Lack of what should be present, synonym of defectus, the opposite of habitus and perfectio