Question: when we yawn why do our eyes water ?

Jonny Brooks-Bartlett answered on 21 Jun 2015:

When people yawn, they tend to tightly shut their eyes, and this does two things. First it squeezes something called the lacrimal duct which causes more tears to flow into the eye. Secondly it squashes closed the tear ducts that drain the tear fluid from the surface of your eye. As a result there are more tears in the eye and nowhere for them to go. So when your yawn ends and you open your eyes again they are watery.