What's the difference between "principal" and "principle"?

You'd be surprised how many people pause before writing "principal" or "principle." They sound exactly the same and look almost identical, so even confident writers second-guess themselves. Here's how to use each one correctly.

Principal

"Principal" has a few meanings. The one you'll hear most often is the head of a school, especially in American English. In the UK, this person is usually called the "head teacher."

• The principal wants to see you in her office.
• Parents can meet the principal after the school concert.

"Principal" can also mean main or most important. This use is fairly formal, and in everyday conversation, most people would say "main."

• Safety is our principal concern.
• The principal reason we chose this flat was the location.

In finance, "principal" is the amount of money you borrow or invest, not counting the interest.

• Each payment covers some interest and some of the principal.

Principle

A "principle" is a basic rule or belief that guides how you think or act. It's always a noun.

• It's against my principles to lie.
• The company was founded on strong ethical principles.
• I don't eat meat, on principle.

It can also mean a basic rule or idea that explains how something works, often in science or law.

• The principle behind solar panels is pretty simple.
• Freedom of speech is one of the basic principles of a democracy.

You'll also hear "in principle" a lot. It means "in general" or "in theory," usually with a "but" coming later.

• In principle, I agree with you, but the timing is bad.

If you need a trick to keep them apart, try this one: the principal of a school is your "pal," and a principle is a rule. Both "principle" and "rule" end in "le."

Want to keep on learning? Check out our Daily Dose of Denglisch Docs for some quick and easy English lessons.