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

To solve this issue, the team created a new tetrathiafulvalene-crown ether COF, named TUS-44, and integrated it with conductive graphene to form a TUS-44@G functional layer for Li-S batteries. — Prabhat Ranjan Mishra, Interesting Engineering, 4 July 2026

Should the luminiferous ether exist, then scientists reasoned that as the Earth orbits the sun at around 66,000 miles per hour (106,216 kilometers per hour), our planet should be moving through the ether, which had been deemed to be stationary. — Robert Lea, Space.com, 3 July 2026

Of course, Nixon has never fully disappeared from the pop culture ether. — Benjamin Svetkey, HollywoodReporter, 16 June 2026

Bitcoin and ether are down 20% and 23%, respectively, in the same period from when the perp was launched on May 18. — Tanaya MacHeel, CNBC, 10 June 2026

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
• 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