hydrogen

American

[hahy-druh-juhn] / ˈhaɪ drə dʒən /

noun

a colorless, odorless, flammable gas that combines chemically with oxygen to form water: the lightest of the known elements. H; 1.00797; 1; density: 0.0899 grams/liter at 0°C and 760 millimeters pressure.

hydrogen British

/ ˈhaɪdrɪdʒən /

noun

1. a flammable colourless gas that is the lightest and most abundant element in the universe. It occurs mainly in water and in most organic compounds and is used in the production of ammonia and other chemicals, in the hydrogenation of fats and oils, and in welding. Symbol: H; atomic no: 1; atomic wt: 1.00794; valency: 1; density: 0.08988 kg/m³; melting pt: –259.34°C; boiling pt: –252.87°C See also deuterium tritium
2. ( as modifier )
  
  hydrogen bomb

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

hydrogen Scientific

/ hī′drə-jən /

The lightest and most abundant element in the universe, normally consisting of one proton and one electron. It occurs in water in combination with oxygen, in most organic compounds, and in small amounts in the atmosphere as a gaseous mixture of its three isotopes (protium, deuterium, and tritium) in the colorless, odorless compound H ₂. Hydrogen atoms are relatively electropositive and form hydrogen bonds with electronegative atoms. In the Sun and other stars, the conversion of hydrogen into helium by nuclear fusion produces heat and light. Hydrogen is used to make rocket fuel, synthetic ammonia, and methanol, to hydrogenate fats and oils, and to refine petroleum. The development of physical theories of electron orbitals in hydrogen was important in the development of quantum mechanics. Atomic number 1; atomic weight 1.00794; melting point −259.14°C; boiling point −252.8°C; density at 0°C 0.08987 gram per liter; valence 1.
See Periodic Table See Note at oxygen

Etymology

Origin of hydrogen

First recorded in 1785–95; from the French word hydrogène; hydro- ¹, -gen

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Compared with normal tissue, cancer cells tend to be more acidic and contain higher levels of hydrogen peroxide.

From Science Daily

Researchers have developed a tiny, battery-powered hydrogen sensor that continuously monitors a wearer’s flatulence, with the aim of collecting data to improve digestive health.

From The Wall Street Journal

The world's first hydrogen double-decker bus fleet has reached the end of the road.

From BBC

Making its production cleaner and more competitive with fossil based hydrogen could accelerate its use not only in heavy industry, but also as a way to store excess renewable energy.

From Science Daily

Oman, which doesn’t, plans to use solar power to create low-carbon exports—hydrogen and products made using it, like steel.

From The Wall Street Journal

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023