hydrogen
noun
hy·dro·gen
ˈhī-drə-jən 
-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
Examples of hydrogen in a Sentence
Recent Examples on the Web
First real-world test of powerful hydrogen turboprop engine The 16-minute test flight covered a distance of about 22 miles (36 kilometers).
—
Sujita Sinha, Interesting Engineering, 6 Apr. 2026
Biological molecules were deconstructed and flattened into a tangled mess of mostly carbon and hydrogen.
—Jeffrey Marlow, New Yorker, 5 Apr. 2026
Workplan topics throughout the year include rate relief measures, energy programs, hydrogen vehicle fueling stations, social media marketing, and long-term power procurement strategy.
—Luke Harold, San Diego Union-Tribune, 5 Apr. 2026
That begs the question, why bother with hydrogen?
—New Atlas, 4 Apr. 2026
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Sujita Sinha, Interesting Engineering, 6 Apr. 2026
Biological molecules were deconstructed and flattened into a tangled mess of mostly carbon and hydrogen.
—Jeffrey Marlow, New Yorker, 5 Apr. 2026
Workplan topics throughout the year include rate relief measures, energy programs, hydrogen vehicle fueling stations, social media marketing, and long-term power procurement strategy.
—Luke Harold, San Diego Union-Tribune, 5 Apr. 2026
That begs the question, why bother with hydrogen?
—New Atlas, 4 Apr. 2026
See All Example Sentences for hydrogen
Cite this Entry
“Hydrogen.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hydrogen. Accessed 8 Apr. 2026.
Copy CitationKids Definition
hydrogen
noun
hy·dro·gen
ˈhī-drə-jən
: 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
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
: 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
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