- Use principle when you're referring to a rule, something established as a standard, or the fundamental cause or origin of something.
- Use principal when you're talking about a quantity of money or the person in charge of an organization, like a school. Principal can also be used as an adjective that means something is of the highest rank.
One way to remember the difference between principle and principal is to call upon TV's most famous principal: Mr. Belding from Saved by the Bell, who reminded his students that "the last three letters in principal spell pal." Aww.
Belding may not have always been on the ball with regard to what was happening in the hallowed halls of Bayside High, but he is useful for helping you remember that if you're talking about a person, you're talking about a principal.