scientific definition of respiration
Definition of RESPIRATION for Kids. 1. : the act or process of breathing: the inhaling of oxygen and the exhaling of carbon dioxide. 2. : the process by which cells use oxygen to break down sugar and obtain energy. the physical and chemical processes (as breathing and diffusion) by which an organism supplies its cells and tissues with the oxygen needed for metabolism and relieves them of the carbon dioxide formed in energy-producing reactions. 3. : cellular respiration.