Ens

Ens is "either ens reale or ens rationis. Ens rationis is that which has no existence but in the idea which the mind forms of it, as a golden mountain. Ens reale, in philosophical language, is taken late et stricte, and is distinguished as ens potentiale, or that which may exist, and ens actuale, or that which does exist. It is sometimes taken as the concrete of essentia, and signifies what has essence and may exist as a rose in winter; sometimes as the participle of esse, and it then signifies what actually exists. Ens without intellect is res a thing." — Fleming, Vocabulary of Philosophy, s.v.