(1) An invisible medium through which all light, heat and electromagnetic waves propagate. Pronounced "ee-ther" with the "th" as in the word "thought," ether was postulated from the 1600s to the 1800s. The word inspired the name Ethernet.|
(2) A group of chemical compounds, the most popular of which is the colorless and transparent diethyl ether, used as a solvent and anesthetic. Diethyl ether was synthesized in the 1500s and named "ether" in the 1700s.