hydrogen
nounUK /ˈhaɪ.drə.dʒən/
US /ˈhaɪ.drə.dʒən/
Hydrogen is the lightest gas in the world and it is in water.
Water is made of hydrogen and oxygen.
OTHER MEANINGS
2. A chemical element with the symbol H and atomic number 1.
Hydrogen is the first element on the periodic table.
3. A colorless, odorless, highly flammable gas used as fuel.
The rocket burns hydrogen to lift off.
4. The lightest and most abundant element in the universe.
Stars are mostly made of hydrogen.