What is the other way to spell principal?

There are two diffferent Words that are homophones (sound-alike Words):

The Word principle applies to a logical premise or to morals.

The physics class studied the principle of expanding gases.

She was person with good principles. She volunteered at the Red Cross every week.

The sound-alike Word principal means "the primary rank," and is the title of the administrative head of some schools. (Children remember this as "the principal is our pal.") It can also mean the base amount of a loan.

The principal export of Kuwait is oil.

Mr. Smith is an elementary school principal.

His payment on his house loan was mostly interest, so the principal was barely reduced.