1. 氧；氧气
Oxygen is a colourless gas that exists in large quantities in the air. All plants and animals need oxygen in order to live.

1. a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas
constitutes 21 percent of the atmosphere by volume
the most abundant element in the earth's crust

Synonym: Oatomic number 8