hydrogen

noun

hy·​dro·​gen ˈhī-drə-jən How to pronounce hydrogen (audio)
-dər-
: a nonmetallic gaseous chemical element with atomic number 1 that is the simplest and lightest of the elements and that is used especially in the processing of fossil fuels and the synthesis of ammonia
—often used before another noun
hydrogen gas
hydrogen atoms
a hydrogen vehicle
the hydrogen industry
 see Chemical Elements Table see also green hydrogen compare deuterium, tritium
hydrogenous
hī-ˈdrä-jə-nəs How to pronounce hydrogen (audio)
adjective

Examples of hydrogen in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
One of those applications is solid oxide electrolysis (SOEC), a hydrogen production technology that uses both electricity and high-temperature steam to improve efficiency compared with conventional electrolysis. — Kaif Shaikh, Interesting Engineering, 4 Aug. 2026 Sometimes, scientists discover new materials by surprise, such as the 2025 discovery of the first gold-hydrogen compound. — Robin MacAluso, The Conversation, 3 Aug. 2026 Fossil-free fertilizer, renewable-hydrogen ammonia that European producers now make at industrial scale, could sharply reduce farmers' exposure to gas prices and geopolitical chokepoints. — Ingmar Rentzhog, Forbes.com, 1 Aug. 2026 But instead of oxygen making up the rest, that remainder is composed of tough-to-breathe methane and molecular hydrogen. — Phil Plait, Scientific American, 31 July 2026 See All Example Sentences for hydrogen

Word History

Etymology

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

First Known Use

1788, in the meaning defined above

Time Traveler
The first known use of hydrogen was in 1788

Phrases Containing hydrogen

Rhymes for hydrogen

See All Rhymes for hydrogen

Browse Nearby Words

hydrogel
hydrogen
hydrogenase
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Cite this Entry

“Hydrogen.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hydrogen. Accessed 6 Aug. 2026.

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Kids Definition

hydrogen

noun
hy·​dro·​gen ˈhī-drə-jən How to pronounce hydrogen (audio)
: a chemical element that is the simplest and lightest of all chemical elements and is normally found alone as a colorless odorless highly flammable gas having two atoms per molecule see element
hydrogenous
hī-ˈdräj-ə-nəs How to pronounce hydrogen (audio)
adjective
Etymology

from French hydrogène "hydrogen," from hydr- "water" and -gène "producer"; so called because when hydrogen gas burns, it combines with oxygen to produce water

Medical Definition

hydrogen

noun
hy·​dro·​gen ˈhī-drə-jən How to pronounce hydrogen (audio)
: 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
hydrogenous
hī-ˈdräj-ə-nəs How to pronounce hydrogen (audio)
adjective

More from Merriam-Webster on hydrogen

Nglish: Translation of hydrogen for Spanish Speakers

Britannica.com: Encyclopedia article about hydrogen

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