Oxygen

Definition

Oxygen (O2) is a colorless, odorless gas that's essential for most forms of life because it's used in the process of respiration to produce energy.

Related terms

Respiration: The process by which cells break down simple food molecules such as glucose and release the energy they contain. Oxygen is crucial for this process.

Oxidation:

A chemical reaction involving the loss of electrons or an increase in oxidation state. Oxygen often plays a role in these reactions.

Atmosphere: The envelope of gases surrounding Earth or another planet. Oxygen makes up about 21% of Earth's atmosphere.