[W/K] :: ROR'

  Ether \E"ther\ ([=e]"th[~e]r), n. [L. aether, Gr. a'iqh`r, fr.
     a'i`qein to light up, kindle, burn, blaze; akin to Skr. idh,
     indh, and prob. to E. idle: cf. F. ['e]ther.] [Written also
     [ae]ther.]
     1. (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.
        [1913 Webster +PJC]
  
     2. Supposed matter above the air; the air itself.
        [1913 Webster]
  
     3. (Chem.)
        (a) 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 an[ae]sthetic. Commonly
            called ethyl ether to distinguish it from other
            ethers, and also ethyl oxide.
        (b) Any similar compound in which an oxygen atom is bound
            to two different carbon atoms, each of which is part
            of an organic radical; as, amyl ether; valeric ether;
            methyl ethyl ether. The general formular for an ether
            is ROR', in which R and R' are organic radicals
            which may be of similar or different structure. If R
            and R' are different parts of the same organic
            radical, the structure forms a cyclic ether.
            [1913 Webster +PJC]
  
     Complex ether, Mixed ether (Chem.), an ether in which the
        ether oxygen is attached to two radicals having different
        structures; as, ethyl methyl ether, C2H5.O.CH3.
  
     Compound ether (Chem.), an ethereal salt or a salt of some
        hydrocarbon as the base; an ester.
  
     Ether engine (Mach.), a condensing engine like a steam
        engine, but operated by the vapor of ether instead of by
        steam.
        [1913 Webster]