Thomas Aquinas and other Catholic theologians have employed the Aristotelian concepts of substance and accident in articulating the theology of the Eucharist, particularly the transubstantiation of bread and wine into body and blood.
[3] To put this in technical terms, an accident is a property which has no necessary connection to the essence of the thing being described.
The nine kinds of accidents, according to Aristotle, are quantity, quality, relation, habitus, time, location, situation (or position), action, and passion ("being acted on").
Together with "substance", these nine kinds of accidents constitute the ten fundamental categories of Aristotle's ontology.
[7] Catholic theologians such as Thomas Aquinas have employed the Aristotelian concepts of substance and accident in articulating the theology of the Eucharist, particularly the transubstantiation of bread and wine into body and blood.