oxygen
//ˈɒksɪdʒən//
Noun
1
A colorless, odorless, tasteless gas that forms about 21% of the Earth's atmosphere and is essential for most forms of life, having the chemical symbol O and atomic number 8.
We need oxygen to breathe and survive.
2
The chemical element with atomic number 8, a member of the chalcogen group in the periodic table.
Oxygen is the eighth element in the periodic table.