Principal and principle are homophones. I’ve come across principal misused more often than principle, but it’s common to get them both confused. Principle is usually a noun but principal can be an adjective or a noun.

Principal

• first in order of importance or value
• the most important or senior person in an organisation

Principle

• a fundamental truth, proposition, rule or law
• a moral rule or set of such morals
• a general scientific theorem or law
• a fundamental source or basis of something

My tip: principal is spelled with an a, which is the first letter in the alphabet – and a principle is often a rule.

Sources:

• Collins English Dictionary (2009)
• Oxford Dictionaries Online
• Pixabay (image)