The element with the chemical symbol 'O' is oxygen. Oxygen is a vital element for life on Earth, comprising about 21% of the Earth's atmosphere. It is essential for respiration in animals and humans, and it is also used in various chemical processes, including combustion. Because of its high reactivity, oxygen forms compounds with nearly all elements and is a crucial part of water (H2O) and organic molecules. In addition to its biological significance, oxygen is used industrially in metal production, chemical synthesis, and in medical applications, including oxygen therapy for patients with respiratory issues.