Somethingsomeone does when they need a big breath of air, or more air in their lungs. Usually it occurs when kids are bored at school.
*yawn* This teacher is so boring, all he talks about is his problems with his wife....geez, do we really need to know this to succeed in life? *yawwwwn* =(
A yawn is an involuntary reflex where the mouth is opened wide, and the lungs take in a lot of air. The air is then exhaled slowly. During this time, the eardrums stretch, and the eyes may also close tight, causing them to water.