hydrogen
//ˈhaɪ.drə.dʒən//
Noun
1
A colorless, odorless, highly flammable gaseous chemical element with the atomic number 1, the lightest and most abundant element in the universe.
Hydrogen is the lightest element in the periodic table.
2
Molecular hydrogen (H₂), used as a fuel or in industrial processes.
Hydrogen is being developed as a clean fuel for cars and buses.