A Part-of-Speech Approach
The word principal, on the other hand, has a variety of meanings as an adjective and as a noun.
Principal as an Adjective
Let’s look first at its single adjectival meaning. As an adjective, principal means “chief” or “main” or “foremost in importance.”
The principal argument in the company’s report tried to ease the fears of investors. The applicant, therefore, satisfied her principal objective: getting a good job. The engineer’s argument fails for one principal reason: a complete absence of any scientific authority supporting it.
Principal as a Noun
Now let’s look at the various meanings of principal in its noun form.
1. The high school principal. Your pal.
2. The key participant in a situation. The principals in the boxing match.
3. A person (the principal) empowering another (the agent) to act in a legal or financial capacity.
4. The perpetrator (the principal) of a crime.
5. The balance due on your mortgage; the relatively small amount of principal you’ve paid when compared with the huge amount of interest.
6. An account or amount of money; the principal of an estate.
7. A principal is also the main rafter supporting a roof.