When proofreading and editing our customers' business documents, we constantly come across the misuse of the words principal and principle.
Many use the phrase "the principal is my pal" to help them remember the difference between the -pal word and the -ple word. This mnemonic works when referring to principal used as a noun meaning "the chief person." It doesn't work for the principal use of principal, which is as an adjective, meaning main, chief, most important. A better rule is to remember that of the two forms, only principal can function as an adjective. Remember the 'a' in principal stands for adjective.
Principle can never be an adjective. It is a noun only, referring to a fundamental law or concept or to a code of conduct, often used in the plural, as in "moral principles."
Here are some examples of the correct usage of principal and principle:
- The principal sum of money on which one draws interest is the principal.
- The principal person in a school is the principal.
- David is a man of principle.
- In this experiment, the principle being applied is conservation of mass.
Once we grasp the principle that principle can never be an adjective, we are less likely to confuse these words!