ether

American  

[ee-ther] / ˈi θər /

Also aether

noun

1. Also called sulfuric ether.  Also called diethyl ether.  Also called ethyl ether,.  Also called diethyl oxide,.  Also called ethyl oxide,.  Chemistry, Pharmacology. a colorless, highly volatile, flammable liquid, C 4 H 10 O, having an aromatic odor and sweet, burning taste, derived from ethyl alcohol by the action of sulfuric acid: used as a solvent and, formerly, as an inhalant anesthetic.

2. Chemistry. (formerly) one of a class of compounds in which two organic groups are attached directly to an oxygen atom, having the general formula ROR.

3. the upper regions of space; the clear sky; the heavens.

4. the medium supposed by the ancients to fill the upper regions of space.

5. Physics. a hypothetical substance supposed to occupy all space, postulated to account for the propagation of electromagnetic radiation through space.

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ether British  

/ ˈiːθə, iːˈθɛrɪk /

noun

1. Also called: diethyl ether.   ethyl ether.   ethoxyethane.  a colourless volatile highly flammable liquid with a characteristic sweetish odour, made by the reaction of sulphuric acid with ethanol: used as a solvent and anaesthetic. Formula: C 2 H 5 OC 2 H 5

2. any of a class of organic compounds with the general formula ROR′ where R and R′ are alkyl groups, as in diethyl ether C 2 H 5 OC 2 H 5

3. the hypothetical medium formerly believed to fill all space and to support the propagation of electromagnetic waves

4. Greek myth the upper regions of the atmosphere; clear sky or heaven

5. a rare word for air

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ether Scientific  

/ ē′thər /

1. An organic compound in which two hydrocarbon groups are linked by an oxygen atom, having the general structure ROR|||PRIMARY_STRESS|||, where R and R|||PRIMARY_STRESS||| are the two hydrocarbon groups. At room temperature, ethers are pleasant-smelling liquids resembling alcohols but less dense and less soluble in water. Ethers are part of many naturally occurring organic compounds, such as starches and sugars, and are widely used in industry and in making pharmaceuticals.

2. A colorless, flammable liquid used as a solvent and formerly used as an anesthetic. Ether consists of two ethyl groups joined by an oxygen atom. Also called diethyl ether, ethyl ether. Chemical formula: C ₄ H ₁₀ O.

3. A hypothetical medium formerly believed to permeate all space, and through which light and other electromagnetic radiation were thought to move. The existence of ether was disproved by the American physicists Albert Michelson and Edward Morley in 1887.

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Other Word Forms

• etheric adjective
• superether noun

Etymology

Origin of ether

First recorded in 1350–1400; Middle English, from Latin aethēr “the upper air, pure air, ether,” from Greek aithḗr, akin to aíthein “to glow, burn,” Old English ād “funeral pyre,” Latin aestus “heat”

Explanation

Ether is a chemical that used to be a common anesthetic that you inhaled before undergoing surgery. In most countries, doctors have replaced it with less flammable, safer drugs. The chemical ether is a colorless liquid that's still used as an anesthetic in some developing countries and as an industrial solvent. The Latin root is aether, which means "the upper pure, bright air." Ether was originally a scientific term for what 19th century physicists called "the fifth element," a substance that was said to fill all space and make up all bodies. In modern times, ether has come to be a literary term that refers to the sky.

Example Sentences

Then the band started up — and the wrong lyrics started playing out of the ether.

From Los Angeles Times • Apr. 2, 2026

So what stuck in people’s minds were those lyrics playing out of the ether.

From Los Angeles Times • Apr. 2, 2026

Bitcoin and ether were trading higher on Tuesday, partially because the quantum risks to crypto may have been mostly priced in, according to Ryan Rasmussen, director and head of research at Bitwise Asset Management.

From MarketWatch • Mar. 31, 2026

Ahead of the selloff, two accounts placed enormous bets that bitcoin and ether would fall.

From The Wall Street Journal • Mar. 26, 2026

It had been four years since he and Emilio Segre had crossed the Berkeley campus with a bucket of ether infused with microscopic quantities of plutonium and suspended from a long wooden pole.

From "Big Science" by Michael Hiltzik