Quick answer: principal means main, chief or the head of a school, while principle means a rule, belief or basic truth. A school principal is your “pal,” and a principle is a “rule” (both end in “le”).
Why People Confuse Them
The two words sound identical and look nearly the same, so even careful writers swap them. Because both are real words, a spell-checker cannot help. The only solution is to know what each one means and to use a simple trick when you write.
Principal: Main or Head
Principal works as both an adjective and a noun.
- Adjective: main or most important. “Cost is the principal reason we chose this plan.”
- Noun (person): the head of a school. “The principal announced a new schedule.”
- Noun (money): the original amount of a loan or investment, before interest. “You still owe the full principal.”
- Noun (role): the lead performer or the person who authorises an agent. “The principal dancer took a bow.”
Principle: Rule or Belief
Principle is only a noun. It describes a fundamental rule, truth or standard of behavior.
- Honesty is a principle I live by.
- The scientist explained the principle of gravity.
- She refused on principle.
Handy Memory Tricks
| Word | Trick |
|---|---|
| Principal | The principal is your pal; also “main” ends in a similar sound to “-al” |
| Principle | A principle is a rule; both end in “-le” |
Common Phrases
- in principle means in theory, as in “In principle, the plan works.”
- on principle means because of a belief, as in “He quit on principle.”
- principal reason means the main reason.
- principal and interest refers to loan payments.
Two Sentences Side by Side
“The principal values honesty” tells us the head of the school has a belief. “The principle is honesty” tells us honesty is the rule. In the first, the word names a person; in the second, it names an idea. If you can replace the word with “head” or “main,” use principal. If you can replace it with “rule” or “belief,” use principle.
Common Mistakes
- “It’s the principle reason” should be principal reason, because it means main.
- “Our school principle” should be principal, because it is a person.
- “A matter of principal” should be principle, because it refers to a belief.
Practice
- The (principal / principle) of the school met the parents.
- Fairness is an important (principal / principle).
- Their (principal / principle) goal is to grow sales.
Answers: principal, principle, principal.
Final Thoughts
Principal means main or head, and principle means rule or belief. Keep the pal-and-rule trick in mind and you can avoid one of the most common errors in English.
