A medium of great elasticity and extreme tenuity, supposed to pervade all space, the interior of solid bodies not excepted, and to be the medium of transmission of light and heat; hence often called luminiferous ether.
- Any of a class of organic compounds in which two hydrocarbon groups are linked by an oxygen atom.
- A volatile, highly flammable liquid, C2H5OC2H5, derived from the distillation of ethyl alcohol with sulfuric acid and used as a reagent and solvent. It was formerly used as an anesthetic. Also called diethyl ether, ethyl ether.
- The regions of space beyond the earth's atmosphere; the heavens.
- The element believed in ancient and medieval civilizations to fill all space above the sphere of the moon and to compose the stars and planets.
- Physics An all-pervading, infinitely elastic, massless medium formerly postulated as the medium of propagation of electromagnetic waves.