Full Idea
Real (as opposed to logical) abstract terms, or at least those which are conceived as real, are either essences or parts of essences, or else accidents (i.e. beings added to a substance).
Gist of Idea
Real (non-logical) abstract terms are either essences or accidents
Source
Gottfried Leibniz (New Essays on Human Understanding [1704], 3.08)
Book Reference
Leibniz,Gottfried: 'New Essays on Human Understanding', ed/tr. Remnant/Bennett [CUP 1996], p.333
A Reaction
Interesting to refer to accidents as 'beings'. This seems to fit abstraction by ignoring, since you can either ignore the accidents to get the essence, or ignore the essence to get the accidents.