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Yawning
The act of producing a yawn, which is an involuntary opening of the mouth, usually accompanied by a movement to take a deep breath. The average yawn lasts about 6 seconds. Yawning sometimes occurs when people become bored, tired depressed, or sleepy. Yawning does not always mean that one is tired, but people who are tired do tend to yawn. Yawning can also occur when vital signs decline, such as after a large amount of blood is lost. Vital signs are measurements of blood flow, body temperature, and breathing, all functions that are essential (vital) for life to continue.

Yawning is thought by some to be a partly automatic response produced by the brainstem in reaction to lower levels of oxygen in the brain. The brainstem is an area in the lower part of the brain that connects it with the spinal cord. This area of the brain controls many functions crucial for life to continue. Yawning can also be caused when the lungs do not get enough oxygen. Seeing other people yawn tends to increase the chance that one will yawn. In fact 55% of people will yawn within five minutes of seeing someone else yawn. Even reading about yawning can make you yawn!

Some people yawn very frequently, a condition known as excessive yawning. Please see our entry for this term to learn more about this condition. Yawning comes from the Middle English word "yanen" meaning "to gape" (open the mouth wide).