Editors cringe when they see the word “principle” being used instead of “principal,” and vice versa.
“Principle” is only a noun, whereas “principal” can be either a noun or an adjective.
A principle is a law, or rule, or concept, or doctrine, or a personal value. An abstract mental construct, if you will.
Example: In spite of being mocked for not smoking, the teen stuck to her principles. “I’m not going to pollute myself,” she said.
A principal is the person or “chief” in charge of a school. Unless the teacher is sending you to the principal’s office for misbehaving, the principal can actually be your friend or “pal.” That’s how I always remember it. The principal (noun) may also be a leading performer, a business leader at a firm, or the primary amount of money that is earning interest.
Used as an adjective, “principal” also means “chief,” or first, or main, or number one, or most important.
Example: The principal use of a water balloon is to get somebody soaking wet — and hopping mad.
If you can substitute the word “chief,” you should spell it with -PAL at the end, because the chief is your pal.
In principle, the principal doesn’t want you to be the principal prankster on April Fool’s Day.