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
The new approach allows hydrogen to be harvested from readily available water sources, including seawater, while maintaining competitive efficiency.
—
Neetika Walter, Interesting Engineering, 9 Feb. 2026
Up to 30 percent of life on Earth doesn’t ever see sunlight; instead these organisms get energy by chowing down on hydrogen generated through chemical interactions between water and rocks.
—Damien Pine, Scientific American, 9 Feb. 2026
But the moonshot was delayed to March because of a hydrogen leak in its Space Launch System rocket, clearing the way for NASA to move up the Falcon 9 space station flight.
—William Harwood, CBS News, 8 Feb. 2026
While working on Copernicus, York was the first researcher to find an isotope of hydrogen known as deuterium inside these clouds.
—Bob Goldsborough, Chicago Tribune, 7 Feb. 2026
See All Example Sentences for hydrogen
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Neetika Walter, Interesting Engineering, 9 Feb. 2026
Up to 30 percent of life on Earth doesn’t ever see sunlight; instead these organisms get energy by chowing down on hydrogen generated through chemical interactions between water and rocks.
—Damien Pine, Scientific American, 9 Feb. 2026
But the moonshot was delayed to March because of a hydrogen leak in its Space Launch System rocket, clearing the way for NASA to move up the Falcon 9 space station flight.
—William Harwood, CBS News, 8 Feb. 2026
While working on Copernicus, York was the first researcher to find an isotope of hydrogen known as deuterium inside these clouds.
—Bob Goldsborough, Chicago Tribune, 7 Feb. 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 14 Feb. 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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