yawn 英[j?:n] 美[j?n]
[例句]A yawn is more contagious than any of these.
When we yawn, we inhale air, and stretch our eardrums, and that is why our ears 'pop' when we yawn. There is a very common misconception about yawning, and that is people yawn when they need more air. But according to research studies, this is not true. Take excercising for an example. When we excerscie, we naturally need to inhale more oxygen, however, we do not yawn more during excercise.
A most likely explanation for why one yawns, is because one needs to cool off one's brain. Our brains require very specific temperatures to operate well, and when we are feeling tired exhausted, our brain temperatures increase, triggering an instict to yawn, and cool off the brain. The intake of air cools the facial blood, hence helping to cool off our brain too.
yawn [j?:n] n. 哈欠;裂口
She yawned during his lecture.
He smothered a yawn behind his hand.
His speech made me yawn.