E3D1
Definition — Part III
Latin
Causam adæquatam appello eam cujus effectus potest clare et distincte per eandem percipi. Inadæquatam autem seu partialem illam voco cujus effectus per ipsam solam intelligi nequit.
English (Elwes 1883)
By an adequate cause, I mean a cause through which its effect can be clearly and distinctly perceived. By an inadequate or partial cause, I mean a cause through which, by itself, its effect cannot be understood.
Modern English
I call a cause adequate when its effect can be clearly and distinctly perceived through it alone. I call a cause inadequate, or partial, when its effect cannot be understood through it alone.