In philosophy, quiddity is identity or "whatness," i.e., something's "what it is." The term derives from the Latin word "quidditas," which was used by the medieval Scholastics to refer to a concept of substance they encountered while translating the works of Aristotle. The (Greek equivalent) term was used by Aristotle in reference to an entity's aspects of "matter" and "form." It describes properties a particular substance (e.g. a person) shares with others of its kind. The question "what (quid) is it?" asks for a general description by way of commonailty. This is quiddity or "whatness" (i.e., its "what it is"). Quiddity is often contrasted with the haecceity or "thisness" of an item, which, in turn, describes the particular properties of an object or substance (e.g. a particular person).