hydrogen
n. uncountablen. the lightest chemical element. It is a gas that has no color or smell and burns very easily.
n. the chemical element with atomic number 1, occurring as a colorless, odorless, highly flammable diatomic gas. It is the most abundant chemical substance in the universe.
Hydrogen is the main fuel for the sun.
Scientists are researching how to use hydrogen as a clean fuel source for cars and buses.
The fusion of hydrogen nuclei into helium within the core of a star releases the immense energy that sustains its luminosity over billions of years.
Borrowed from French hydrogène (“hydrogen”), coined by the French chemists Louis-Bernard Guyton de Morveau (1737–1816) and Antoine Lavoisier (1743–1794) from hydro- (prefix meaning ‘water’) + -gène (suffix denoting a producer of something), from the fact that water is produced as a compound when hydrogen is oxidized. The prefix hydro- is borrowed from Ancient Greek ῠ̔δρο- (hŭdro-), from ῡ̆̔́δωρ (hū̆́dōr, “water”), ultimately from Proto-Indo-European wed- (“water”). The suffix -gène is borrowed from Ancient Greek -γενής (-genḗs, suffix meaning ‘born in a certain condition or place’), from γένος (génos, “descendant, offspring; race; etc.”) (ultimately from Proto-Indo-European ǵenh₁- (“to beget, produce; to give birth”)) + -ης (-ēs, suffix forming some third-declension adjectives). By surface analysis, hydro- (prefix meaning ‘water’) + -gen (suffix denoting a producer of something).
Uncountable when referring to the element or gas; occasionally countable in chemistry when referring to specific isotopes or atoms.