Which is correct?
The _________ reason to buy PictBridge-compliant devices is convenience.
Principal means foremost or most important. We were taught to remember that with the handy phrase “The principal is your pal.” But you can imagine how often we kids repeated that to each other — especially without air quotes.
A principle, on the other hand, is a rule, standard or guideline.
Grammar Girl covers principal vs. principle in more detail.
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