hydrogen

noun hy·dro·gen \ ˈhī-drə-jən , -dər- \

|Updated on: 17 Jul 2018

Definition of hydrogen

: a nonmetallic element that is the simplest and lightest of the elements, is normally a colorless odorless highly flammable diatomic gas, and is used especially in synthesis — see Chemical Elements Table — compare deuterium, tritium

—

hydrogenous

play \hī-ˈdrä-jə-nəs\ adjective

See hydrogen defined for English-language learners

See hydrogen defined for kids

Recent Examples of hydrogen from the Web

The light arose from the collision between a remarkably energetic neutrino – a wraithlike subatomic particle moving close to the speed of light – and the nucleus of a hydrogen or oxygen atom deep within the ice.

— eoin o'carroll, The Christian Science Monitor, "Neutrino demonstration heralds a new way of observing the cosmos," 12 July 2018
Researchers believe that about half of the carbon remains in its pure form while the rest of it binds with hydrogen, creating either greasy aliphatic carbon or gaseous naphthalene, the stuff used in mothballs.

— jason daley, Smithsonian, "Our Galaxy Is Really Greasy and Smells Like Moth Balls," 28 June 2018
Previously, Cassini detected lighter, gassy molecules such as methane and ethane, which contain one or two carbon atoms and a smattering of hydrogens; these molecules weigh in at around 15 atomic mass units.

— National Geographic, "Right Stuff for Life Found on Small Saturn Moon," 27 June 2018
The money would buy hydrogen fuel cell buses for AC Transit’s fleet, reducing pollution along bus routes in the East Bay.

— rachel swan, SFChronicle.com, "In fighting California gas tax, national Republicans see rallying point," 26 June 2018
The basis of the project is to remove oxygen from carbon dioxide in order to create more oxygen in the atmosphere as well as an alternate fuel source in hydrogen.

— staff report, chicagotribune.com, "Shout Out: Nelson Fernandes, science enthusiast and aspiring engineer," 20 June 2018
Introduced in 1909, the pH scale — officially, the power of hydrogen — measures the acidity or alkalinity of a substance.

— casey quackenbush, Time, "Google Doodle Celebrates S.P.L. Sørensen, the Trailblazing Chemist Behind the pH Scale," 29 May 2018
But the sun will remain relentless, as spots of clouds will hover overhead but don't count on much respite from that burning ball of hydrogen in the sky.

— eder campuzano, OregonLive.com, "Portland Saturday weather: Clear skies and highs nearing 80 (once the clouds go away)," 12 May 2018
White dwarfs, for instance, are the shrunken, cooling and superdense remains of sun-sized stars that have run out of hydrogen to fuse.

— The Economist, "For the first time, astronomers have a reliable map of the heavens," 26 Apr. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'hydrogen.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of hydrogen

French hydrogène, from hydr- + -gène -gen; from the fact that water is generated by its combustion

NEW! Time Traveler

First Known Use: 1788

in the meaning defined above

See Words from the same year

HYDROGEN Defined for English Language Learners

hydrogen

noun

Definition of hydrogen for English Language Learners

: a chemical element that has no color or smell and that is the simplest, lightest, and most common element

HYDROGEN Defined for Kids

hydrogen

noun hy·dro·gen \ ˈhī-drə-jən \

Definition of hydrogen for Students

: a colorless, odorless, and tasteless flammable gas that is the lightest of the chemical elements

History for hydrogen

When hydrogen is burned it combines with oxygen to make water. That fact accounts for the name of this gas. The word hydrogen was formed from two Greek roots. The first, hydro-, means “water,” and the second, -gen, means “giving rise to, producing.”

Medical Dictionary

hydrogen

noun hy·dro·gen \ ˈhī-drə-jən \

medical Definition of hydrogen

: a nonmetallic element that is the simplest and lightest of the elements and that is normally a colorless odorless highly flammable diatomic gas —symbol H — see deuterium, tritium — Chemical Elements Table

—