form

In Greek and medieval European philosophy, that which makes a thing what it is. For Plato, a Form was an immaterial, independent object, which could not be perceived by the senses and was known only by reason; thus, a horse was a thing participating in the Form of horseness. For Aristotle, forms existed only in combination with matter: a horse was a lump of matter having the form of a horse - that is, the essential properties (see essence) and powers of a horse. However, Aristotle, like the medieval philosophers after him, does not make it clear whether there is a different form for each individual, or only for each type or species.

In Platonic philosophy Form is generally capitalized and is synonymous with his use of idea.