superoksiidanioon (O₂•-), vesinikperoksiid (H₂O₂), hüdroksüülradikaal (OH•) ja singletne hapnik (¹O₂), Reactive oxygen species (ROS) are chemically reactive chemical species containing oxygen. Examples include superoxide (O₂•-), peroxides (H₂O₂), hydroxyl radical (OH•) , and singlet oxygen (¹O₂). ROS may damage other substances in a cell as they are strong oxidizers, but they can also act as a signal molecule.