What is (a) A property or quality of a thing which is not essential to it, as whiteness in paper; an attribute. (b) A quality or attribute in distinction from the substance, as sweetness, softness called?

accident — (Log.) (a) A property or quality of a thing which is not essential to it, as whiteness in paper; an attribute. (b) A quality or attribute in distinction from the substance, as sweetness, softness. (Webster's 1913.)

Sources