Principal vs. Principle: Commonly Confused Words

Portrait of male teacher with arms folded in school corridor
The word principal can refer to the leader of a school. Phil Boorman / Getty Images

Principle and principal are homophones, which means that they sound alike but have different meanings. Principal refers to something or someone of importance, whereas principle refers to a basic truth or law.

How to Use Principle

Principle is a noun that means basic truth, law, rule, or assumption. It can refer to rules of proper conduct, fundamental doctrines, or other views about right and wrong that govern an individual's conduct. The word principle is often used in relation to the concept of morality.

You probably hear about specific principles on a regular basis. Innocent until proven guilty is a principle of the U.S. legal system. A farmer might decide to use only organic pesticides because using pesticides goes against their principles.

If you consider yourself a law-abiding person, you would not call yourself a principle. Instead, you would be a person of principle.

How to Use Principal

Principal, on the other hand, can be used as both a noun and an adjective. In both cases, it is used to designate something, or someone, of importance. As a noun, principal has more than ten definitions. Some of the most frequently-used of those definitions are:

  • A leader or head of an organization or institution, typically a school. 
  • The non-interest portion of a loan. For example, if you took out a loan of $100,000, the principal would be $100,000.
  • A leader or owner of a business. If you owned your own business or were a high-level individual at a firm, you would be considered a principal.

As an adjective, the word means first, or highest in rank. For instance, your principal complaint when seeing a doctor might be a stomach ache, or the principal actors on the set are the ones with leading roles. In the latter case, “principal actors” could even be condensed to “principals” as they are the people in the starring roles.

Principal can also be turned into the adverb principally, meaning “for the most part.” If you were principally a children’s book author, it would mean you primarily wrote children’s books, but might venture into other genres or have a side-career.

Examples

The following examples further clarify the differences between the two terms. 

  • The principal goal of this article is to help you master the difference between two words. Here, principal is used to convey the fact that this goal is the first and primary one of the article. the first and primary purpose of the article. Principle cannot be used here, first because it cannot be used as an adjective and second because it does not mean "first" or "primary."
  • The high school principal wants all students to learn the fundamental principles of math. Principal is used here to connote that this individual is the leader of the school. Principles refers to the most important concepts in the field of mathematics. 
  • The principal speaker’s insistence on equal disabled access at the event was a matter of principleHere, principal is used to show that the speaker is the primary and most important speaker at the event. Principle is used to show that the speaker believes allowing disabled access is the only morally correct course of action. 
  • As an environmentalist, he refused to use plastic bags on principle. In this sentence, principle is used to express that the refusal to use plastic bags is part of the subject's conception of right and wrong.

    How to Remember the Difference

    To remember the difference between these two terms, pay attention to the last three letters. Principal ends with -pal. Think of leaders and principals as being your friend and offering guidance. It can also serve as a reminder that principal can refer to a “pal,” or a person, whereas principle refers to rules or tenets. Also, keep in mind that principle is always a noun and will never be used as an adjective. Principal can be a noun or an adjective, but in either case will typically signal something or someone of importance.