the fifth and highest element after air and earth and fire and water; was believed to be the substance composing all heavenly bodies

[ Syn: quintessence ]

any of a class of organic compounds that have two hydrocarbon groups linked by an oxygen atom

a medium that was once supposed to fill all space and to support the propagation of electromagnetic waves

[ Syn: aether ]

a colorless volatile highly inflammable liquid formerly used as an inhalation anesthetic

[ Syn: ethoxyethane , divinyl ether , vinyl ether , diethyl ether , ethyl ether ]