It is a simple two lettered word. But I find it difficult to use this word most of the times. I almost avoid using it in many situations but even in the few instances that I use this word, it somehow gets ignored.
When you want to say it without being rude, people don't even listen to it.
To use this word, one needs to have the patience to explain the situation n convince others. To me, convincing people is the most difficult job.
The worst part in saying 'no' is, whether it is accepted or ignored, the result is only unhappiness. In the first case, when people unhappily accept a 'no' , it doesn't give a feeling of achievement or victory to the one who has uttered the word 'no' but leaves them unhappy too. In the second case, if one's opinion got ignored, it would definitely hurt.
There should be a way to avoid this word and handle the situation with better and polite words which won't hurt anybody.
P.S.: My vocabulary is too bad to find one such word.