Circumstantiae actuum humanorum accidentia eorum dicenda sunt quia quod est extra substantiam rei ad rem ipsam pertinens, accidens eius dicitur.
The circumstances of human acts should be called their accidents because what is outside a thing's substance, while it belongs to that thing, is called its accident.
Nomen circumstantiae ab his quae in loco sunt, derivatur ad actus humanos. Dicitur autem in localibus aliquid circumstare, quod est quidem extrinsecum a re, tamen attingit ipsam, vel appropinquat ei secundum locum. Et ideo quaecumque conditiones sunt extra substantiam actus, et tamen attingunt aliquo modo actum humanum, circumstantiae dicuntur.
The word "circumstance" has passed from located things to human acts. Now in things located, that is said to surround something, which is outside it, but touches it, or is placed near it. Accordingly, whatever conditions are outside the substance of an act, and yet in some way touch the human act, are called circumstances.
Particulares conditiones cuiuslibet rei singularis dicuntur accidentia individuantia ipsam. Sed philosophus, in III Ethic., circumstantias nominat particularia, idest particulares singulorum actuum conditiones. Ergo circumstantiae sunt accidentia individualia humanorum actuum.
The particular conditions of any singular thing are called its individuating accidents. But the Philosopher (Ethic. iii, 1) calls the circumstances particular things [ta kath' ekasta], i.e., the particular conditions of each act. Therefore the circumstances are individual accidents of human acts.