Just to clarify

PRINCIPAL: primary or main: The principal reason Columbus sailed to America was to find a trade route. Also, the head of a school: Principal Skinner was caught with his pants down again.

PRINCIPLE: 1. an accepted or professed rule of action or conduct: a person of good moral principles.
2. a fundamental, primary, or general law or truth from which others are derived: the principles of modern physics.
3. a fundamental doctrine or tenet; a distinctive ruling opinion: the principles of the Stoics.

Okay? Dictionary.com is your friend.

That is all.