Principal vs Principle



One of the trickiest things in English to get right are homophones, or words that sound the same but are spelled differently and have different meanings. In the case of principle and principal, do you know the difference? Which one can be used as an adjective as well as a noun?

This post will explain the difference between these two words and give examples to show when to use which one!

The Meanings + Related Forms

Both principal and principle come from the same root word in Latin, primus, or prime. The two words are linked, which accounts for their distinct but similar meanings.


Principal has two meanings, one as an adjective and the other as a noun. However, they have the same pattern: they mean something or someone that is a leader, the first, and/or the most important.

  • Noun: the head, chief, or leader; the leader of a school; the initial sum of an investment
  • Adjective: the most important, the chief; referring to the initial sum of an investment


Principle is always a noun, unless the word is in a different form.

  • Noun: A truth or idea that serves as the foundation for something, such as a belief, behavior, or moral code; an accepted rule for conduct

Principled is the adjective form of principle. It simply describes something (a person, moral code, etc.) that is founded on principles.



  • The principal objective of this internship is to introduce the company to you.
  • The principal of the school called me into her office yesterday.
  • I turned my principal investment of $3,000 into $4,000!


  • It’s not that this situation is unacceptable in itself. It’s the principle of the matter! What happens if customers want us to do this every time?
  • That person doesn’t even care about legal principles; she just says what she wants.
  • The marketing approach seems good in principle but I don’t think it will actually work out for us.

How to Tell Which One to Use

Telling which word to use is not too difficult after you understand the difference in the meanings of the two words.

When to Use Principal

  • If the word describes a person, always use principal.
  • If the word describes an initial sum of money, use principal.
  • If the word means important, first, essential, etc., use principal.

When to Use Principle

  • If the word describes an idea, such as a theory or belief, use principle.
  • If the word follows “in” or “on”, use principle.

How to Remember

A great way to remember the difference is that principal contains “pal”! Your principal (a person) can be your pal, and your pal is one of the first and most important people in your life. If you remember this, you can remember the meaning of principal!

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