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 compare deuterium, tritium
Examples of hydrogen in a Sentence
Recent Examples on the Web
In this setup, hydrogen is injected into the combustion chamber as air is being compressed, along with a small quantity of pilot fuel such as biodiesel, which is used to initiate ignition and the consequent combustion of hydrogen with air.
—
David Blekhman, Forbes.com, 21 July 2025
The team also theorizes that this star has not yet begun to burn hydrogen in its core, the process that defines the main sequence lifetime of a star.
—Robert Lea, Space.com, 21 July 2025
Chevron, Exxon and others are investing in projects to produce hydrogen fuel.
—Spencer Kimball, CNBC, 3 July 2025
On the sustainability front, Silver Nova is equipped with a large-scale hybrid power source, which combines hydrogen fuel cells, batteries, and dual engines that run on LNG.
—AFAR Media, 3 July 2025
See All Example Sentences for hydrogen
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David Blekhman, Forbes.com, 21 July 2025
The team also theorizes that this star has not yet begun to burn hydrogen in its core, the process that defines the main sequence lifetime of a star.
—Robert Lea, Space.com, 21 July 2025
Chevron, Exxon and others are investing in projects to produce hydrogen fuel.
—Spencer Kimball, CNBC, 3 July 2025
On the sustainability front, Silver Nova is equipped with a large-scale hybrid power source, which combines hydrogen fuel cells, batteries, and dual engines that run on LNG.
—AFAR Media, 3 July 2025
See All Example Sentences for hydrogen
Cite this Entry
“Hydrogen.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hydrogen. Accessed 25 Jul. 2025.
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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