When Martin Luther King jr. said “In the end, we will remember not the words of our enemies, but the silence of our friends”, he not only spoke about the silent moments with companions but also spoke of the presumably rotten words uttered by enemies.
Importance that silence actually holds is revealed when it is broken. We often think about moments when we should have been silent, we think of ourselves as foolish when we say things that end up either hurting the person on his face or when the third party finds out what was said about him.
Words may give meaning, but the actual depth is felt in silence. Silence usually is accompanied by gestures; for example in hospitals when the visitor can only hold the hands of the coma tic patient. Here no words can beat the result of silence.
In anger, the most common gesture is a bad word, but the most effective is silence.
On the other hand, maintaining silence in court room when truth lies with you is not an act of power but the one of a sinner. Same way when miss communication arises among colleagues and friends, its best to speak up and patch things up.
Tom Blair describes the beauty and importance as “Silence is one of the great arts of conversation, as allowed by Cicero himself, who says, 'there is not only an art, but an eloquence in it.' A well bred woman may easily and effectually promote the most useful and elegant conversation without speaking a word. The modes of speech are scarcely more variable than the modes of silence.”

