ether

noun

• 1 Chemistry a pleasant-smelling colourless volatile liquid that is highly flammable. It is used as an anaesthetic and as a solvent or intermediate in industrial processes.

  • Alternative names: diethyl ether, ethoxyethane; chemical formula: C₂H₅OC₂H₅
• [count noun] any organic compound with a similar structure to ether, having an oxygen atom linking two alkyl or other organic groups:methyl t-butyl ether

• 2 (also aether) chiefly literary the clear sky; the upper regions of air beyond the clouds:nasty gases and smoke disperse into the ether
• (the ether) informal air regarded as a medium for radio:choral evensong still wafts across the ether

• 3 (also aether) Physics, archaic a very rarefied and highly elastic substance formerly believed to permeate all space, including the interstices between the particles of matter, and to be the medium whose vibrations constituted light and other electromagnetic radiation: the motion of the planets would be retarded by the ether through which they moved