response to reactive oxygen species Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a reactive oxygen species stimulus. Reactive oxygen species include singlet oxygen, superoxide, and oxygen free radicals. GO:0000302 biological_process response to AOS response to ROI response to ROS response to active oxygen species response to reactive oxidative species response to reactive oxygen intermediate