Nouns

(n)quintessence, etherthe fifth and highest element after air and earth and fire and water; was believed to be the substance composing all heavenly bodies
(n)etherany of a class of organic compounds that have two hydrocarbon groups linked by an oxygen atom
(n)ether, aethera medium that was once supposed to fill all space and to support the propagation of electromagnetic waves
(n)ether, ethoxyethane, divinyl ether, vinyl ether, diethyl ether, ethyl ethera colorless volatile highly flammable liquid formerly used as an inhalation anesthetic