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

The concept naturally arose of the ether as a frictionless, incompressible, homogeneous, invisible substance that pervaded all space like a transparent jelly.

—Martin Gardner

b

: airwaves

broadcasting radio signals into the ether

etheric

i-ˈther-ik 

-ˈthir-

adjective

Examples of ether in a Sentence

The balloon disappeared into the ether.

Recent Examples on the Web

Stock Chart IconStock chart icon Price of bitcoin and ether over the past year. —Krysta Escobar, CNBC, 5 Nov. 2025

The rapid proliferation and growth of spot ETFs like those for bitcoin and ether – as well as the potential for dozens more once regulatory operations resume at full capacity – also ties into another important change. —Sean Stein Smith, Forbes.com, 18 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

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

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