Sometimes people feel sleepy.They can't stay interested in what they are doing and they open their mouths wide quickly.We call this a yawn.It makes a pretty silly face.Why do people do it?Scientist do not know much about yawns.But they have some ideas.Our bodies get tired.Our minds get tired,too.A tired mind needs air.So we yawn.The quick yawn takes in air.And the air wakes up our mind.But not for long.Watch out!Here comes another yawn.
