hy·​dro·​gen | \ ˈhī-drə-jən How to pronounce hydrogen (audio) , -dər-\

Definition of hydrogen

: 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 — see Chemical Elements Table — compare deuterium, tritium

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Other Words from hydrogen

hydrogenous \ hī-​ˈdrä-​jə-​nəs How to pronounce hydrogenous (audio) \ adjective

Examples of hydrogen in a Sentence

Recent Examples on the Web

Some of this airborne table salt reacts chemically with hydrogen in the water vapor, creating the hydrochloric acid. Nsikan Akpan, Scientific American, "Kilauea’s Lava Is Now Spilling into the Ocean. Here’s Why That’s Dangerous," 22 May 2018 But for stars closer in size to the sun, there's an end stage where—when all the hydrogen reserves are spent—the star expands outward, shredding planets in the path. John Wenz, Popular Mechanics, "Scientists Think They've Found a Dead Planetary Core Orbiting a Dead Star," 4 Apr. 2019 Acetylene is widely used in the production of other chemicals, and Xinhua said Haipoer planned to use the delivery to make hydrogen. Josh Chin, WSJ, "Truckload of Acetylene Explodes Near Chemical Factories in China," 28 Nov. 2018 Titan's atmosphere is comprised of 98.4 percent nitrogen, 1.6 percent methane and 0.1-0.2 percent hydrogen. Chris Ciaccia, Fox News, "Alien life on Saturn's moon? Dust storms on Titan spotted for the first time," 25 Sep. 2018 For any hydrogen to survive without getting incorporated into larger atomic nuclei, the scientists found a different fundamental constant would have to be smaller. Charles Q. Choi, Space.com, "Why Alternate Universes Might Also Host Life Around their Stars," 26 Sep. 2018 Carrying that much fuel (89 truckloads of liquid oxygen, 28 trailer-loads of liquid hydrogen, and 27 rail cars full of kerosene) caused a number of problems with combustion stability. Alex Hollings, Popular Mechanics, "The Saturn V Story: From Nazi Roots to America's Moon Rocket," 6 Feb. 2019 Further Reading California amends rules to push vehicles toward hydrogen, electricity, biofuel Biofuel, which is predominantly made from corn in the US, is a political minefield in the Trump Administration. Megan Geuss, Ars Technica, "EPA reconsidering biofuel targets after production goals are missed," 25 Nov. 2018 While carbon, hydrogen, and nitrogen are common components of smoke, many of the compounds found in wildfire smoke haven’t even been identified yet — but researchers are working on that. Mary Beth Griggs, The Verge, "Scientists fly through plumes of wildfire smoke to unravel its mysteries," 21 Nov. 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.

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First Known Use of hydrogen

1788, in the meaning defined above

History and Etymology for hydrogen

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

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Statistics for hydrogen

Last Updated

24 Apr 2019

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Time Traveler for hydrogen

The first known use of hydrogen was in 1788

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English Language Learners Definition of hydrogen

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


hy·​dro·​gen | \ ˈhī-drə-jən How to pronounce hydrogen (audio) \

Kids Definition of hydrogen

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


hy·​dro·​gen | \ ˈhī-drə-jən How to pronounce hydrogen (audio) \

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

Other Words from hydrogen

hydrogenous \ hī-​ˈdräj-​ə-​nəs How to pronounce hydrogenous (audio) \ adjective

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More from Merriam-Webster on hydrogen

Spanish Central: Translation of hydrogen

Nglish: Translation of hydrogen for Spanish Speakers

Britannica English: Translation of hydrogen for Arabic Speakers

Britannica.com: Encyclopedia article about hydrogen

Comments on hydrogen

What made you want to look up hydrogen? Please tell us where you read or heard it (including the quote, if possible).


to move or proceed with twists and turns

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