"Principle" versus "principal."
I’m sure we’ve all lain awake in the wee hours, tossing and turning, and pondered the deep issues—such as the distinction between “principle” and “principal.” The starting point for analyzing this sleep-depriving puzzle is to know that “principle” is almost always a noun (with exceptions too weird to explain here), and that “principal” is usually an adjective (although it can be a noun, e.g., Principal Skinner, or even an adverb if modified with –ly).
Ok, maybe that wasn’t such a helpful starting point. Let’s continue.
Generally, a “principle” is a fundamental law, rule, doctrine, or code of conduct that must be followed, e.g.,
Einstein’s Principle of Equivalence (used to derive important results without having to solve the full equations of General Relativity).
The Principle of Charity (a presumption made in philosophy in which preconceptions about an argument, a topic, or a belief are set aside in the attempt to gain new understanding).
Stare decisis is legal principle that obliges judges to respect the precedents established by prior decisions.
The “Golden Rule” is a consistency principle that states, “You must treat others in the same way that you would want to be treated in the same situation.”
Note that the noun “principle” can become a verb by adding –ed, e.g., “Seeking a principled distinction.” Now let’s turn to “principal.”
A “principal” is a word with many meanings. When used as an adjective, is means something that is the “main,” or highest in rank or importance, e.g.,
HonestCo’s principal legal argument was that the contract term was unambiguous.
Van Gogh’s principal medium was oil on canvas.
A faulty steering linkage was the principal reason for the crash.
Finally, “principal” can also be used as a noun, e.g., Principal Skinner, principal and interest, and principal and agent; or when –ly is added, it becomes an adverb, e.g., “Van Gogh was principally a post-Impressionist painter.”
So in summary, a “principle” is a noun that connotes a fundamental law, rule, or general truth. A “principal” is an adjective (or sometimes a noun) that conveys the meaning of “main” or “primary”—or if used as a noun, “main or chief one.”
That is all for now …