Yawn

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, 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.

Etymology

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 gap (compare the figura etymologica in Norse ginnunga-gap) gum "palate" and gasp (via Old Norse), Latin hiō, hiatus, and Greek chasm, chaos.