When you breathe, you inhale and exhale. In other words, you breathe in and out. When you breathe out, you exhale.
If you exhale on a cold winter day, your breath looks like smoke in the frigid air. Yoga classes, with their emphasis on breathing, involve a lot of inhaling and exhaling. When you exhale, your lungs push air out, reducing the carbon dioxide in your body and making room for you to inhale oxygen. The Latin root exhalare combines ex, "out," and halare, "breathe."