Nouns adjective are the words which express quality considered as qualifying, or, as the schoolmen say, in concrete with, some particular subject. Thus the word _green_ expresses a certain quality considered as qualifying, or as in concrete with, the particular subject to which it may be applied. Words of this kind, it is evident, may serve to distinguish particular objects from others comprehended under the same general appellation. The words _green tree_, for example, might serve to distinguish a particular tree from others that were withered or blasted. Prepositions are the words which express relation considered, in the same manner, in concrete with the co-relative object. Thus the prepositions _of_, _to_, _for_, _with_, _by_, _above_, _below_, _&c._ denote some relation subsisting between the objects expressed by the words between which the prepositions are placed; and they denote that this relation is considered in concrete with the co-relative object. Words of this kind serve to distinguish particular objects from others of the same species, when those particular objects cannot be so properly marked out by any peculiar qualities of their own. When we say, _the green tree of the meadow_, for example, we distinguish a particular tree, not only by the quality which belongs to it, but by the relation which it stands in to another object. As neither quality nor relation can exist in abstract, it is natural to suppose that the words which denote them considered in concrete, the way in which we always see them subsist, would be of much earlier invention, than those which express them considered in abstract, the way in which we never see them subsist. The words _green_ and _blue_ would, in all probability, be sooner invented than the words _greenness_ and _blueness_; the words _above_ and _below_, than the words _superiority_ and _inferiority_. To invent words of the latter kind requires a much greater effort of abstraction than to invent those of the former. It is probable, therefore, that such abstract terms would be of much later institution. Accordingly, their etymologies generally show that they are so, they being generally derived from others that are concrete.