The element with the chemical symbol 'O' is oxygen. Oxygen is essential for life, as it is a critical component of water and plays a crucial role in cellular respiration in most living organisms. It is a colorless, odorless gas that makes up about 21% of the Earth's atmosphere and is highly reactive, forming compounds with many other elements. Oxygen can exist in diatomic form as O₂ and is vital for combustion processes. In addition to its biological significance, oxygen is also used in various industrial processes, including the production of steel and other materials.