What is might?

[The Witch-King of Angmar]

Hi.

I wanted to know what "might" is in Tolkien's books. He always writes "XX was the mightiest of the ..". In the Silmarillion it is almost in every chapter that a specific person is mightiest or strongest or .. I don't know.

So, I simply wanted to know, what might is.

In the LOTR it is written, that Gandalf was really mighty, but what was it? He didn't show his might very often. Once when he spoke the spell of command when the Balrog was on the other side of the door.

Or in the Silmarillion, Chapter Of the Maiar is written, that Eonwe was the mightiest in Arms in Arda.

And so on ..

Thanks.