Definition of hydrogens:
(n) :
The lightest chemical element (symbol H), with an atomic number of 1 and atomic weight of 1.008.
(n) :
Molecular hydrogen (H₂), a colourless, odourless and flammable gas at room temperature.
(n) :
An atom of the element.
(n) :
The isotope hydrogen-1 (protium) (symbol H or ¹H), contrasting with deuterium and tritium
(n) :
A molecule of this molecular species
(n) :
A sample of the element/molecule.