clear; obvious; unequivocal · sensible; reasonable · to understand; to realize

I don't know at all why he quit his job suddenly.

The professor was unable to comprehend what I meant.

I don't quite understand what he says.

I have no idea what you mean.

And I know you didn't do this just to win an election. And I know you didn't do it for me. You did it because you understand the enormity of the task that lies ahead. For even as we celebrate tonight, we know the challenges that tomorrow will bring are the greatest of our lifetime: two wars, a planet in peril, the worst financial crisis in a century.