Lewis Short
(P. a.) : accĭdens, entis.
* Fr. accĭdo.
* As subst. n.
* The accidental, nonessential quality of any thing, τò συμβεβηκός (opp. substantia, the Greek οὐσία): causa, tempus, locus, occasio . . . rerum sunt accidentia, the accidental or extraneous circumstances, Quint. 5, 10, 23; so 3, 6, 36; 4, 2, 130: ex accidentibus (= epithetis), id. 8, 3, 70; hence,an adjective,Macr. S. 1, 4.
* An accident or chance.
* In gen., Dig. 35, 2, 51: per accidens, accidentally, Firm. Math. 5, 4.
* In part., an unfortunate circumstance: accidentia (opp. prospera), Pseudo-Quint. Decl.
Charlton T. Lewis, Charles Short, A Latin Dictionary