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.

---

noun

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

---

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.

---

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 ).

Related Words

See capital ¹.

Other Word Forms

• principalship noun
• underprincipal noun

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

“I’ll put the odds of a deal in the next 10 days at 90%,” says Brian McCarthy, managing principal of Macrolens, a boutique investment-research firm in Massachusetts.

From MarketWatch • Apr. 18, 2026

Kieren Jessop, principal analyst at Omdia, notes that a normal prelaunch “stockout” usually shows reduced availability across all configurations, not just high-memory ones—more support for the likelihood of unanticipated interest.

From The Wall Street Journal • Apr. 17, 2026

Finally, the series rests on the shoulders of the three principal players, who are just a pleasure to watch; the camera obliges by moving in close.

From Los Angeles Times • Apr. 15, 2026

“Whether that marks the start of a rebalancing, or early anticipation of de-escalation, will be the key question for the sector in the weeks ahead,” said Kenneth Lamont, a principal at Morningstar.

From Barron's • Apr. 15, 2026

“Patricia?” said Dr. Rosalia Lopez, the district school superintendent, after she found the Riverview principal in the bleachers.

From "The Smartest Kid in the Universe" by Chris Grabenstein

Related Words

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