So, how do you spell principal? Or is it principle? Both are right? How do you know which to use and when?
What does each mean and what is the correct usage? Let’s take a look at an example of why there might be some confusion:
The principal’s principal principle is to pay down debt principal following the debt avalanche principle.
Can you believe that is a valid sentence? @!#*%$ing English, right?
Let’s take a look at the various meanings and some guidelines for deciding which spelling to use. I can’t promise to help you get it right every time, but I bet after reading this you’ll get the correct usage almost every time.
Note: This post is from the original location of this site: PrincipalFI.com. I kept it because I’ve been told it’s useful, even after the site name change!
Definitions of Principal and Principle
Let’s go to the authorities first for a review of each word. There are a number of online resources for definitions, but I really appreciate Merriam-Webster’s social media game so we’ll use theirs. (Seriously, if you aren’t following this dictionary on Twitter – do it! And – who would have thought I’d ever ask anyone to follow a dictionary…)
PRINCIPAL
Principal (adjective)
- most important, consequential, or influential
Principal (noun)
- A person who has controlling authority or is in a leading position
- A matter or thing of primary importance
- A capital sum earning interest, due as a debt, or used as a fund
- The corpus of an estate, portion, devise, or bequest
Financial principal
- In finance, principal refers to the face amount of a debt instrument or an amount of money borrowed.
Synonyms
I always understand more through comparison to other words. It is particularly helpful in this case.
Synonyms for principal include: primary, number one, highest, preeminent
PRINCIPLE
- a comprehensive and fundamental law, doctrine, or assumption
- b: a rule or code of conduct
- habitual devotion to right
principles the laws or facts of nature underlying the working of an artificial device
Synonyms
Synonyms for principle include: law, standard, axiom, rule, truth
So Which Do I Use?
Looking at actual definitions is useful! But let’s try and simplify it more to help you remember without needing to look it up. Here are the big ideas behind principal and principle. With pictures to connect your memory!

A person. If you are referring to a person, use PRINCIPAL. Always.
This is easy to remember – the principal is your pal. (shout out to famous children’s author Beverly Clearly)
Especially in the case of a school principal, of course!

Primary or first. When referring to the first or most important of something, use PRINCIPAL.

Money. If you are referring to money use PRINCIPAL.
Examples include mortage principal, the principal amount of investment, or the principal remaining on a debt.

E is for Ethical If you are referring to someone who follows laws, rule, or acts ethically – they are principled.


Laws, guidelines, or axioms. To refer to something that someone should do according to a certain set of advice or rule use PRINCIPLE.
Got it? Let’s Review and Apply
Let’s breakdown that horrific sentence again with a note to each of the above categories.

The principled (ethics) principal’s (person) principal (primary or first) principle (guideline) is to pay down debt principal (money) following the debt avalanche principle (rule/axiom).
Two simple groupings help me keep it straight almost every time:
People, money, and first are principal.
Rules and guidelines are principle.
One more try to hook your memory. This works for me every time now:
Principle ends with L and E. If it’s a reference to
Everything else is principal.
Did this help? You can practice or test out your newfound expertise with a simple online test.
There you go! A quick, but hopefully helpful guide to the eternal question that I know haunts you: is it principal or principle?
I used to teach it as a Principal is your main money man. 🙂
That’s a good one!