Aristotle's Accidents

An accident (Greek συμβεβηκός), in metaphysics and philosophy, is a property that the entity or substance has contingently, without which the substance can still retain its identity. An accident does not affect its essence.

The term "accident" is not as used as in common speech, i.e., a chance incident, normally harmful.

Aristotle, proposes an ontology of substances and accidents. Substances, such as a man or a horse, are the basic, independent, entities in this ontology; accidents are the dependent entities that inhere in the substances.

Aristotle made a distinction between the essential and accidental properties of a thing.

Nine kinds of accidents according to Aristotle

Quantity
Quality
Relation
Habitus
Τime
Location
Situation (or position)
Action
Passion ("being acted on").

Together with "substance", these nine kinds of accidents constitute the ten fundamental categories of Aristotle's ontology.