* Dioxygen (O2): This is the most common form of oxygen, making up about 21% of the Earth's atmosphere. It is a colorless, odorless, and tasteless gas that is essential for respiration.
* Ozone (O3): Ozone is a highly reactive molecule that is found in the stratosphere, where it protects life on Earth from harmful ultraviolet radiation. It is a pale blue gas with a pungent odor.
There are also some less stable forms of oxygen, such as singlet oxygen and atomic oxygen, but these are not considered stable forms.
