Principal has two main meanings that sound exactly alike but mean very different things:

1. The leader of a school. The principal manages teachers, makes important decisions, and helps create a safe learning environment. When students get sent to the principal's office, it usually means there's a problem that needs attention. A helpful way to remember this spelling: the principal is your pal.
2. The original amount of money in a loan or investment, separate from any interest. If you borrow $1,000 from the bank, that $1,000 is the principal. When you pay back the loan, part of each payment reduces the principal while another part pays the interest (the fee for borrowing). Understanding principal helps explain why saving money early matters: in a savings account, your principal earns interest, and then that interest becomes part of your principal, earning even more interest over time.

The word can also mean “main” or “most important,” as in “the principal reason I joined the science club was to build robots.” This usage connects to both meanings: the principal of a school is the main person in charge, just like the principal in a loan is the main amount of money.