\E"ther\, n. [L. aether, Gr. ?, fr. ? 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, 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}.
2. Supposed matter above the air; the air itself.
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
       powerful solvent of fats, resins, and pyroxylin, but
       finds its chief use as an an[ae]sthetic. Called also
       {ethyl oxide}.
   (b) Any similar oxide of hydrocarbon radicals; as, amyl
       ether; valeric ether.
{Complex ether}, {Mixed ether} (Chem.), an oxide of two
   different radicals in the same molecule; 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.