n. The upper air; the blue heavens. It was supposed by Aristotle to extend from the fixed stars down to the moon.n. In astronomy and physics, a hypothetical medium of extreme tenuity and elasticity supposed to be diffused throughout all space (as well as among the molecules of which solid bodies are composed), and to be the medium of the transmission of light and heat. See the extract.n. In chem.: One of a class of organic bodies divided into two groups: Simple ethers, consisting of two basic hydrocarbon radicals united by oxygen, and corresponding in constitution to the metallic oxids, as CH3OCH3, methylether, or methyloxid, analogous to AgOAg, silver oxid. Compound ethers, consisting of one or more basic or alcohol radicals and one or more acid hydrocarbon radicals united by oxygen, and corresponding to salts of the metals, as CH3COO C2H5, ethyl acetate, or acetic ether, corresponding to CH3COONa, sodium acetate. Also called estersn. Specifically, ethyl oxid or ethyl ether (C2H5)2O, also called, but improperly, sulphuric ether, because prepared from a mixture of sulphuric acid and alcohol.n. See the adjectives.An obsolete form of either.A dialectal variant of edder.n. A dialectal form of adder.