ether

noun

ˈē-thər 

1

a

: the rarefied element formerly believed to fill the upper regions of space

b

: the upper regions of space : heavens

2

a

: a light volatile flammable liquid C₄H₁₀O used chiefly as a solvent and especially formerly as an anesthetic

b

: any of a class of organic compounds characterized by an oxygen atom attached to two carbon atoms

3

a

or less commonly aether

ˈē-thər 

: a medium that in the wave theory of light permeates all space and transmits transverse waves

b

: airwaves

etheric

i-ˈther-ik 

-ˈthir-

adjective

Examples of ether in a Sentence

The balloon disappeared into the ether.

Recent Examples on the Web

For a long time, traditional financial instutions have stayed away from cryptocurrencies like bitcoin and ether. —Arjun Kharpal, CNBC, 13 Oct. 2025

In the past 24 hours, roughly $5 billion of bitcoin has been liquidated, along with about $4 billion of ether and about $2 billion of solana, according to CoinGlass. —Auzinea Bacon, CNN Money, 11 Oct. 2025

Physicists invented ether as a medium through which light waves traveled. —Dipangkar Dutta, The Conversation, 3 Oct. 2025

Everything is ether, including the ground beneath your feet. —Andy Andersen, Vulture, 18 Sep. 2025

Word History

Etymology

Middle English, from Latin aether, from Greek aithēr, from aithein to ignite, blaze; akin to Old English ād pyre — more at edify

First Known Use

14th century, in the meaning defined at sense 1a

Phrases Containing ether

• diethyl ether
• ether extract
• ethyl ether
• into the ether
• over/through the ether
• the ether

Kids Definition

ether

noun

ˈē-thər 

1

a

: an invisible substance once believed to fill the upper regions of space

b

: the upper regions of space : heavens

2

: an easily evaporated flammable liquid used chiefly to dissolve other substances and especially formerly as an anesthetic

Medical Definition

ether

noun

ˈē-thər 

1

: a medium that in the wave theory of light permeates all space and transmits transverse waves

2

a

: a light volatile flammable liquid C₄H₁₀O used especially formerly chiefly as an anesthetic

called also diethyl ether, ethyl ether, ethyl oxide

b

: any of various organic compounds characterized by an oxygen atom attached to two carbon atoms