Grammar Lesson Monday: Principle and Principal

Welcome to Grammar Lesson Monday!
This continuous series will address many common grammar mistakes made in the media and that I've seen more than once.  I strive to make the world a better place with good grammar.

Today, we will learn about principle and principal.

Principle is always a noun, meaning a rule, law, standard, or doctrine.
The key principle in this lesson is to use good grammar.
He is a man of principle (meaning he has set personal standards and doesn't waver from them).

Principal is either a noun or an adjective, meaning of the highest rank or importance, or main.
My principal is the principal advocate for education in my city.

That's it for today.  Celebrate good grammar!