A yawn is a reflex action that involves opening the mouth wide and inhaling deeply, often followed by a slow exhalation. It is commonly associated with tiredness, boredom, or the need for increased oxygen. Yawning can occur in response to seeing someone else yawn, a phenomenon known as contagious yawning. Yawning is believed to help regulate brain temperature and increase alertness. It can also be a way for the body to signal a transition between different states of activity, such as moving from wakefulness to sleep. While often seen as a sign of fatigue, yawning can occur in various situations, including during stress or boredom.