Yawning is oftem menfestation of lack of of interest in ongoing activities.  It may also reflect sleepiness. 

Yawning is linked with Boredom which is the result of  monotony. Doing the same thing mechanically leads to monotony. Ultimately this shows up in the form of Yawning.

Tiredness and boredom are the common reasons for yawning. Another interesting thing is that yawning is ‘contagious’. That means you will have an urge for yawning when you see others yawning. Even thinking about yawning or seeing an image of a person yawning will make you yawn. 

You have added one more thing for this discussion. Yes, yawning is contagious. Another reason for yawning is doing the same thing and also doing a work which is not liked by you.contribute in a big way besides other factors..

Yawn is series of bodily motion which is practiced by humans even before they born. It is an epidemic as when some one yawn, it is followed by rest of people present there. 

Yes. Yawn is contagious. Yawn is the outcome of monotony in your work or surroundings.

Yawning is contagious as I yawn when I see someone yawning. The best thing to avoid is to indulge yourself in the things you are interested in.

Yawning is an indication of Monotony. Avoid sticking to same work. Try different variations.

I think yawn may not be a polite opinion but certainly it is honest to yawn at certain environment. 

Yawning is treated as an impolite action which expresses Boredom. Which is why many hide their Yawning with hands.