principal

American  

[prin-suh-puhl] / ˈprɪn sə pəl /

adjective

1. first or highest in rank, importance, value, etc.; chief; foremost.

   The principal problem is a lack of money.

   She's the principal advisor on the council.

   Synonyms:

   preeminent, cardinal, main, leading, paramount, prime

   Antonyms:

   ancillary, secondary

2. of, of the nature of, or constituting principal or capital.

   Though our portfolio has seen losses, the principal investment remains untouched.

3. Geometry. (of an axis of a conic) passing through the foci.

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noun

• principals
  plural

1. a chief or head.

   Synonyms:

   leader

2. the head or director of a school or, especially in England, a college.

   Synonyms:

   master, dean, headmaster

3. a person who takes a leading part in any activity, as a play; chief actor or doer.

4. the first player of a division of instruments in an orchestra (excepting the leader of the first violins).

5. something of principal or chief importance.

6. Law.

   1. a person who authorizes someone else, such as an agent, to represent them.

   2. a person directly responsible for a crime, either as an actual perpetrator or as an abettor present at its commission.

7. a person primarily liable for an obligation, in contrast with an endorser, or the like.

8. the main body of an estate, or the like, as distinguished from income.

9. Finance. a capital sum, as distinguished from interest or profit.

10. Music.

    1. an organ stop.

    2. the subject of a fugue.

11. (in a framed structure) a member, as a truss, upon which adjacent or similar members depend for support or reinforcement.

12. each of the combatants in a duel, as distinguished from the seconds.

principal British  

/ ˈprɪnsɪpəl /

adjective

1. first in importance, rank, value, etc; chief

2. denoting or relating to capital or property as opposed to interest, etc

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noun

1. a person who is first in importance or directs some event, action, organization, etc

2. (in Britain) a civil servant of an executive grade who is in charge of a section

3. law

   1. a person who engages another to act as his agent

   2. an active participant in a crime

   3. the person primarily liable to fulfil an obligation

4. the head of a school or other educational institution

5. (in Scottish schools) a head of department

6. finance

   1. capital or property, as contrasted with the income derived from it

   2. the original amount of a debt on which interest is calculated

7. a main roof truss or rafter

8. music

   1. the chief instrumentalist in a section of the orchestra

   2. one of the singers in an opera company

   3. either of two types of open diapason organ stops, one of four-foot length and pitch and the other of eight-foot length and pitch

9. the leading performer in a play

principal Cultural  

1. The original amount of money lent, not including profits and interest.

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Commonly Confused

The noun principle and the noun and adjective principal are often confused. Although pronounced alike, the words are not interchangeable in writing. A principle is broadly “a rule of action or conduct” ( His overriding principle is greed ) or “a fundamental doctrine or tenet” ( Their principles do not permit the use of alcoholic beverages ). The adjective principal has the general sense “chief, first, foremost”: My principal objection is the cost of the project. The noun principal has among other meanings “the head or director of a school” ( The faculty supported the principal in her negotiations with the board ) and “a capital sum, as distinguished from interest or profit” ( The monthly payments go mostly for interest, leaving the principal practically untouched ).

Synonym Usage

See capital ¹.

Other Word Forms

Derived Forms

• principalship
  noun
• underprincipal
  noun

Inflected Forms

Nouns

• principals
  plural

Etymology

Origin of principal

First recorded in 1250–1300; Middle English, from Latin prīncipālis “first, chief,” equivalent to prīncip- ( see prince) + -ālis -al ¹

Explanation

For an adjective that points to the main or most important thing, your best choice is principal. Is your principal goal for the summer to have fun or to earn some extra money? The word, principal, comes from the Latin principalis "first in importance" and is related to the title of prince. You can see the relation when you think about its meanings — the head of a school, the starring actor in a film, and the client of an agent. Don't confuse principal with its homophone principle, a moral rule or law of nature. If you talk about a country's principal exports, you mean the main ones.

Example Sentences

See Examples For:

principal principals

"So the question was, 'Why on Earth is this gene so active in microglia?'" recalled Dr. Polleux, a principal investigator at the Zuckerman Institute.

From Science Daily ● Sep. 1, 2026

At the Maria Cabrales school, principal Regla Maria Perera, 64, said there is an art to running a school that has no electricity and is not blessed with good natural light.

From Barron's ● Sep. 1, 2026

The picks were named co-CEOs while Overdeck and Siegel remained Two Sigma’s principal owners and co-chairmen, though Overdeck reappointed himself to the management committee last year.

From The Wall Street Journal ● Aug. 31, 2026

Norris says his loyalty to McLaren is based on the relationships he has within the team - starting with chief executive officer Zak Brown and team principal Andrea Stella - and their shared history.

From BBC ● Aug. 29, 2026

It’s probably a good thing that I spilled the beans beforehand, because we’re pretty quiet and respectful when the principal makes the announcement.

From "Linked" by Gordon Korman

Francois Resnais, national secretary of SNPDEN-Unsa, France's top union of school principals, criticised the timing as "bad".

From Barron's ● Aug. 24, 2026

Among the principals, everyone—El-Sayed, Stevens, Chuck Schumer, the Democratic Senatorial Campaign Committee—quickly got on the same team.

From Slate ● Aug. 8, 2026

Also praising Chait during that April gathering in City Hall was Maria Nichols, president of Associated Administrators of Los Angeles, which represents schools principals and assistant principals among others.

From Los Angeles Times ● Jun. 24, 2026

His extensive reporting for “Checkmate,” including the cooperation of its principals, gives the book a page-turning intimacy.

From The Wall Street Journal ● Jun. 3, 2026

The next day at work I called my former principals at Tembisa and Alexandra Secondary School and requested letters of recommendation.

From "Kaffir Boy: An Autobiography" by Mark Mathabane

Related Words

• dominant
• key
• leading
• main
• major
• outstanding
• paramount
• predominant
• preeminent
• primary
• prime
• prominent