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(as modifier): hydrogen bomb
WordReference Random House Learner's Dictionary of American English © 2025
hy•dro•gen /ˈhaɪdrədʒən/USA pronunciation
n. [uncountable]
WordReference Random House Unabridged Dictionary of American English © 2025- Chemistrya colorless, odorless gas that burns easily, and combines chemically with oxygen to form water.
hy•dro•gen
(hī′drə jən),USA pronunciation n.
- Chemistrya colorless, odorless, flammable gas that combines chemically with oxygen to form water: the lightest of the known elements. Symbol: H;
at. wt.: 1.00797;
at. no.: 1;
density: 0.0899 g/l at 0°C and 760 mm pressure.
- French hydrogène. See hydro-1, -gen
- 1785–95
Collins Concise English Dictionary © HarperCollins Publishers::
'hydrogen' also found in these entries (note: many are not synonyms or translations):
-gen
- A star
- B star
- Balmer
- Balmer series
- Bohr theory
- Brackett series
- Cavendish
- DNA
- H
- H-bomb
- Haber process
- acetylide
- acid
- acid radical
- acid soil
- active hydrogen
- alkoxide
- alkylation
- alpha helix
- aluminum borohydride
- amide
- amine
- amino acid
- ammonia
- antihydrogen
- aprotic
- arseniuretted hydrogen
- arsine
- aryl group
- arylamine
- atomic
- atomic hydrogen
- atomic mass
- atomic weight
- barium peroxide
- base pair
- base-pairing rules
- basicity
- benzene ring
- benzene series
- bismuthine
- bisulfate
- bisulfite
- bisulphate
- bitartrate
- bomb
- bond
- borane
- buildup