Emily Dickinson Lexicon

AB'STRACT, a. [L. abstractus.]

1. Separate; distinct from something else. An abstract idea, in metaphysics, is an idea separated from a complex object, or from other ideas which naturally accompany it; as the solidity of marble contemplated apart from its color or figure. – Encyc. Abstract terms are those which express abstract ideas, as beauty, whiteness, roundness, without regarding any subject in which they exist; or abstract terms are the names of orders, genera, or species of things, in which there is a combination of similar qualities. – Stewart. Abstract numbers are numbers used without application to things, as 6, 8, 10: but when applied to any thing, as 6 feet, 10 men, they become concrete. Abstract or pure mathematics, is that which treats of magnitude or quantity, without restriction to any species of particular magnitude, as arithmetic and geometry; opposed to which is mixed mathematics, which treats of simple properties, and the relations of quantity, as applied to sensible objects, as hydrostatics, navigation, optics, &c. – Encyc.
2. Separate, existing in the mind only; as an abstract subject; an abstract question; and hence, difficult, abstruse.