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Principals and Principles

Is your school principal principled? What is your principal principle? In my editing work, I’ve noticed that writers often use 'principal' when they mean 'principled' and vice versa. In this post, I’ll provide some clarity on the usage of both words.

Avoid mistakes with my guide to similar-sounding words, available only to site members.


The Point

  • Principal can function as a noun referring to a person in charge or an adjective meaning most important.

  • Principle is a noun referring to an idea.



"Principal" comes from the Latin principalis (first, original). It can function as either a noun or adjective. When used as a noun, it most often refers to "a person who has controlling authority or is in a leading position": The principal called me about my child’s inappropriate behavior. It can also refer to money that is earning interest or that is owed: The interest was added to the principal. As an adjective, it means "most important, consequential, or influential": My principal concern is your well-being.


"Principle," which has the same Latin prefix as "principal"—princip- (first or chief)—is derived from principium (source) and principia (foundations). It is always a noun, and most commonly refers to "a comprehensive and fundamental law, doctrine, or assumption" or a "rule or code of conduct": I am committed to the principle of social justice. A closely related word, "principled," is an adjective meaning "exhibiting, based on, or characterized by principle": The politician was unusually principled. Another "word" I sometimes see—"principaled" or "principalled"—is not actually a word.

Using the correct word in your class paper, dissertation, or article is important to properly conveying your meaning as well as appearing professional. Unfortunately, your spell checker won't catch these mistakes, nor will many grammar checkers (although a good proofreader will). Therefore, it is important to have a good understanding of when to use each. Of course, there are a number of other pairs that writers often use incorrectly. That's why I developed Ten Sets of Similar-Sounding Word Pairs: A Usage Guide. It is available exclusively to site members, so sign up today for a FREE membership!

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