an element more pure and subtle than air; the matter of the highest region above. This fluid has been considered by the ancients, and many modern philosophers, to be diffused throughout the universe. With reference to the motions of the celestial bodies, it has been termed the etherial medium. Newton believed in the existence of such a fluid.

Chemistry, an extremely volatile and inflammable fluid, produced by the distillation of alcohol with an acid. According to the acid employed in its preparation, it receives the names of nitric ether, sulphuric ether, &c.; but when perfectly rectified, the ether is the same whatever acid has been used. See Chemistry.