Aether

noun

1. The substance formerly supposed to fill the upper regions of the atmosphere above the clouds, in particular as a medium breathed by deities.
2. Often as aether and more fully as luminiferous aether: a substance once thought to fill all unoccupied space that allowed electromagnetic waves to pass through it and interact with matter, without exerting any resistance to matter or energy; its existence was disproved by the 1887 Michelson–Morley experiment and the theory of relativity propounded by Albert Einstein (1879–1955).
3. The atmosphere or space as a medium for broadcasting radio and television signals; also, a notional space through which Internet and other digital communications take place; cyberspace.
4. A particular quality created by or surrounding an object, person, or place; an atmosphere, an aura.
5. Diethyl ether (C4H10O), an organic compound with a sweet odour used in the past as an anaesthetic.