Boss is always right but sometimes he is wrong. What is better ,silence or Convey him about his mistake?

Just try to convey him/her don't force.

always give your view point,,, leave the decision on him

You may easily convey him by positive and calm attitude while demonstrate pros and cons. 

Please do not take it as someone's mistake. Taking it as an opportunity to share learning and giving it as an opportunity to others to learn would be more fruitful.

This would be possible if at the beginning all would have mutually made an understanding to allow space for their opinions, making it as a source of learning and development.

I've had the pleasure of working under the guidance of two real leaders in that case. Both my Ceo's have always valued team input, and that perhaps is the difference between a boss and a true leader. The final decision whether right or wrong had always been the bosses but it feels amazing that someone of such high calibre is so open to listen to his prodigies.

If the Boss thinks that he is always right, then he is not a good leader and manager.  He has to be very open-minded and listen to ideas and opinion. I'm a very straight forward person. i will lay down cards on the table, open my ideas, thoughts and opinion.  Now, if my boss will just put these things in the garbage can then, it's his problem, as long as it's all documented. 

I believe if the relationship between the manager and the employee or employees, was good, then I would prefer that the employee tell the manager his wrong. But, never directly tell him that 'he was wrong', in an indirect way, say that doing such a thing is not good or not professional.

First explain him if he doesn't understand Explain the same situation to your subordinate in front of your boss(Unknowingly that boss is in front of you),If he is sensible he will understand that he is wrong..

I  may convey him my honest opinion but I will be cautious enough to choose the right words in polite manner even in private or in a certain  public work place.

Though embarrassing in his part, if it's constantly practice at work,  my boss will certainly rely in me on some certain extent and it will create transparency between us.

only one action you can do:-

you can tolde him ( what you think if we do1-2-3 )

how come (always right) and (but sometimes is wrong). It does not come together.

 

Anyway, in your job description there is no mention to mentor your boss but to follow your JD. Your boss will be the one to be blamed and bear the responsibility. Your role here is to learn from his mistakes and gain experience so when you are in his foot, you will commit the same mistakes