ether Definition

ether
noun

1. Any of a group of organic chemical compounds formed by the dehydration of alcohols, that are volatile and highly flammable, and contain two hydrocarbon groups linked by an oxygen atom.
2. (formula C₂H₅OHC₂H₅) the commonest ether, widely used as a solvent, and formerly employed as an anaesthetic.

Form: diethyl ether (also)
3. physics.
A hypothetical medium formerly believed to be necessary for the transmission of electromagnetic radiation, a concept abandoned when the theory of relativity was accepted.
Form: aether (also)
4. poetic
The clear upper air or a clear sky.
Form: aether (also)

Etymology: 17c: from Greek aither the heavens.