ether

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of a class of organic compounds in which two hydrocarbon groups are linked by an oxygen atom.
2. n. 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.
3. n. The regions of space beyond the earth's atmosphere; the heavens.
4. n. 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.
5. n. Physics An all-pervading, infinitely elastic, massless medium formerly postulated as the medium of propagation of electromagnetic waves.

Century Dictionary and Cyclopedia

1. n. The upper air; the blue heavens. It was supposed by Aristotle to extend from the fixed stars down to the moon.
2. 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. The phenomena of Light are best explained as those of undulations; but undulations, even in the most extensive use of the term, as signifying any periodic motion or condition whose periodicity obeys the laws of wave motion, must be propagated through some medium. Heat, while passing through space, presents exactly the same undulatory character, and requires a medium for its propagation. Electrical attraction and repulsion are explained in far the most satisfactory way by considering them as due to local stresses in such a medium. Current electricity seems due to a throb or series of throbs in such a medium, when released from stress. Magnetic phenomena seem due to local whirlpools, set up in such a medium. … We are led to infer, therefore, that there is such a medium, which we call the Luminiferous Ether, or simply the Ether; that it can convey energy; that it can present it at any instant, partly in the form of kinetic, partly in that of potential energy; that it is therefore capable of displacement and of tension; and that it must have rigidity and elasticity. Calculation leads us to infer that its density is (Clerk Maxwell) that of water, or equal to that of our atmosphere at a height of about 210 miles, a density vastly greater than that of the same atmosphere in the interstellar spaces, and that its rigidity is about that of steel; hence, that it is easily displaceable by a moving mass, that it is not discontinuous or granular, and hence that as a whole it may be compared to an impalpable and all pervading jelly through which Light and Heat waves are constantly throbbing, which is constantly being set in local strains and released from them, and being whirled in local vortices, thus producing the various phenomena of Electricity and Magnetism, and through which the particles of ordinary matter move freely, encountering but little retardation, if any, for its elasticity, as it closes up behind each moving particle, is approximately perfect. A. Daniell, Prin. of Physics, p. 208.
3. 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 esters
4. n. Specifically, ethyl oxid or ethyl ether (C₂H₅)₂O, also called, but improperly, sulphuric ether, because prepared from a mixture of sulphuric acid and alcohol. Ether is a light, mobile, colorless liquid having a characteristic refreshing odor and burning taste. It is highly volatile and inflammable. It is chiefly used as an anesthetic agent, by inhalation. The ordinary ether of the United States Pharmacopœia consists of 74 per cent., and the stronger (ether fortior) of 94 per cent., of ethyl oxid.
5. n. See the adjectives.
6. An obsolete form of either.
7. A dialectal variant of edder.
8. n. A dialectal form of adder.

Wiktionary

1. n. organic chemistry, countable A compound containing an oxygen atom bonded to two hydrocarbon groups.
2. n. organic chemistry, uncountable Diethyl ether (C4H10O), a compound used as an early anaesthetic.
3. n. uncountable A classical physical element, considered as prevalent in the heavens and inaccessible to humans. In some versions of alchemy, this was the fifth element in addition to air, earth, fire and water.
4. n. archaic, physics, uncountable A substance (aether) once thought to fill all space that allowed electromagnetic waves to pass through it and interact with matter, without exerting any resistance to matter or energy (disproved by Einstein in his Theory of Relativity).
5. n. The sky or heavens; the upper air.

GNU Webster's 1913

1. n. (Physics) A medium of great elasticity and extreme tenuity, once 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. It is no longer believed that such a medium is required for the transmission of electromagnetic waves; the modern use of the term is mostly a figurative term for empty space, or for literary effect, and not intended to imply the actual existence of a physical medium. However. modern cosmological theories based on quantum field theory do not rule out the possibility that the inherent energy of the vacuum is greater than zero, in which case the concept of an ether pervading the vacuum may have more than metaphoric meaning.
2. n. Supposed matter above the air; the air itself.
3. n. A light, volatile, mobile, inflammable liquid, (C2H5)2O, of a characteristic aromatic odor, obtained by the distillation of alcohol with sulphuric acid, and hence called also sulphuric ether. It is a powerful solvent of fats, resins, and pyroxylin, but finds its chief use as an anæsthetic. Commonly called ethyl ether to distinguish it from other ethers, and also ethyl oxide.
4. n. Any similar compound in which an oxygen atom is bound to two different carbon atoms, each of which is part of an organic radical

WordNet 3.0

1. n. any of a class of organic compounds that have two hydrocarbon groups linked by an oxygen atom
2. n. a medium that was once supposed to fill all space and to support the propagation of electromagnetic waves
3. n. the fifth and highest element after air and earth and fire and water; was believed to be the substance composing all heavenly bodies
4. n. a colorless volatile highly inflammable liquid formerly used as an inhalation anesthetic