Medical Definition of Yawn
Yawn: Involuntary opening of the mouth, accompanied by slowly breathing inward and then outward. Repeated yawning can be a sign of drowsiness, boredom, or depression. The yawn helps to open tiny air sacs (alveoli) in the lungs that can collapse during shallow breathing.Source: MedTerms™ Medical Dictionary
Last Editorial Review: 6/9/2016
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