To respire means to breathe, taking air into your lungs and then releasing it. Every time you inhale oxygen and exhale carbon dioxide, you're respiring. All animals respire: dogs pant after running, fish move water through their gills, and whales surface to breathe through their blowholes.

Scientists use respire when they're talking about breathing in a precise, technical way. Your science teacher might explain that your cells need oxygen to produce energy, and that this process of taking in oxygen and releasing carbon dioxide is called respiration. Plants respire too, though they also make oxygen through photosynthesis.

Respire sounds more formal than simply saying “breathe.” You'd probably tell a friend “I can't breathe” after sprinting, but a doctor might say that a patient “respired normally” during an examination. The respiratory system includes your lungs, nose, throat, and all the parts of your body involved in breathing.