Yawn

Yawn
Joseph Ducreux pandiculating (both yawning and stretching); self-portrait c. 1783
Organisms	Vertebrates
Biological system	Nervous system
Health	Unaffected or Beneficial
Action	Involuntary
Stimuli	Fatigue Boredom Stress Sleepiness Others yawning Mirror neuron reflex
Method	Complete extension of jaw, inhalation, eyes close, stretching of the eardrums, exhalation
Duration	6 seconds

A yawn is a reflex consisting of the simultaneous inhalation of air and the stretching of the eardrums, followed by an exhalation of breath.

Yawning (oscitation) most often occurs in adults immediately before and after sleep, during tedious activities and as a result of its contagious quality. It is commonly associated with tiredness, stress, sleepiness, or even boredom and hunger, though studies show it may be linked to the cooling of the brain. In humans, yawning is often triggered by others yawning (e.g. seeing a person yawning, talking to someone on the phone who is yawning) and is a typical example of positive feedback. This "contagious" yawning has also been observed in chimpanzees, dogs, birds, and reptiles, and can occur across species. Approximately 20 physiological reasons for yawning have been proposed by scholars, but there is little agreement about its main functions.

During a yawn, the tensor tympani muscle in the middle ear contracts, creating a rumbling noise from within the head.

English yawn continues a number of Middle English forms, yanen from Old English ġānian, and yenen, yonen from Old English frequentatives ġinian, ġionian, from a Germanic root *gīn-. The Germanic root has Indo-European cognates, from a root *g̑hēi- found also with -n- suffix in Greek χαίνω "to yawn", and without the -n- in English (compare the figura etymologica in Norse ginnunga-gap) "palate" and (via Old Norse), Latin hiō, hiatus, and Greek chasm, chaos.

The Latin term used in medicine is oscitatio (anglicized as ), from the verb oscito "to open the mouth". is the act of yawning and stretching simultaneously.