- a substance hypothesized by the ancients as filling all space beyond the sphere (noun) of the moon, and making up the stars and planets
- the upper regions of space; clear sky
- Rare the air
- Chem. any of a series of organic compounds having an oxygen atom linking two carbon atoms from two hydrocarbon radicals, generally ROR; esp., ethyl ether, a volatile, colorless, highly flammable liquid, HCOCH, prepared by the reaction of sulfuric acid and ethyl alcohol and used as an anesthetic and a solvent for resins and fats
- Physics a hypothetical diffuse, invisible medium formerly thought to pervade space and transmit light, heat, etc.
Origin of etherMiddle English from Classical Latin aether from Classical Greek aith?r from aithein, to kindle, burn from Indo-European base an unverified form aidh- from source Classical Latin aestas, summer, Old English ætan, to burn