Principal or principle?
principal is an adjective meaning “Primary; most important; first level in importance”; principle is a noun meaning “A fundamental assumption, fundamental law or guiding belief”. Use principal as an adjective and principle as a noun (principal is also a noun: “The money originally invested or loaned, on which basis…”). They sound the same (/ˈpɹɪn.sɪ.pəl/). In written English (wordfreq, 2021 data) principal is about 1.5 times as common as principle.
What is the difference between principal and principle?
| principal | principle | |
|---|---|---|
| Part of speech | adjective, noun | noun, verb |
| Meaning | Primary; most important; first level in importance Chosen or assumed among a branch of possible values of a multi-valued function so that the function is single-valued The money originally invested or loaned, on which basis interest and returns are calculated | A fundamental assumption, fundamental law or guiding belief A rule used to choose among solutions to a problem To equip with principles; to establish, or fix, in certain principles; to impress with any tenet or rule of conduct |
| Example | Smith is the principal architect of this design | We need some sort of principles to reason from |
| Forms | none | principles |
| Pronunciation | /ˈpɹɪn.sɪ.pəl/ [ˈpɹɪn.sɪ.pɫ̩] /ˈpɹɪn.sə.pəl/ | /ˈpɹɪn.sɪ.pəl/ [ˈpɹɪn.sɪ.pɫ̩] /ˈpɹɪn.sə.pəl/ |
| In writing | 33 times per million words | 22 times per million words |
Sources: principal and principle in the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
Every current meaning of principal and principle
principal
- 1
Primary; most important; first level in importance
Smith is the principal architect of this design
- 2
The money originally invested or loaned, on which basis interest and returns are calculated
A portion of your mortgage payment goes to reduce the principal, and the rest covers interest
- 3
Chosen or assumed among a branch of possible values of a multi-valued function so that the function is single-valued
Two is the principal square root of 4. Both −2 and +2 are square roots of 4
- 4
AustraliaCanadaUSThe chief administrator of a school
- 5
CanadaUKThe chief executive and chief academic officer of a university or college
- 6
A legal person that authorizes another (the agent) to act on their behalf; or on whose behalf an agent or gestor in a negotiorum gestio acts
When an attorney represents a client, the client is the principal who permits the attorney, the client′s agent, to act on the client′s behalf
- 7
The primary participant in a crime
- 8
Either party in a duel
principle
- 1
A fundamental assumption, fundamental law or guiding belief
We need some sort of principles to reason from
- 2
To equip with principles; to establish, or fix, in certain principles; to impress with any tenet or rule of conduct
- 3
A rule used to choose among solutions to a problem
The principle of least privilege holds that a process should only receive the permissions it needs
- 4
Moral rule or aspect
I don't doubt your principles
- 5
A rule or law of nature, or the basic idea on how the laws of nature are applied
Bernoulli's principle
- 6
A fundamental essence, particularly one producing a given quality
Many believe that life is the result of some vital principle
- 7
A chemical compound within plant or animal tissue that is characteristic of it and more or less peculiar to it, such that it defines the character of that tissue from a human viewpoint (as for…
the active principle
- 8
A source, or origin; that from which anything proceeds; fundamental substance or energy; primordial substance; ultimate element, or cause
Source: the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); obsolete, archaic, dialect and rare senses left out.
Which is more common, principal or principle?
principal appears 33 times per million words; principle 22 times per million words.
principal 33 times per million wordsprinciple 22 times per million words
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How many people search principal vs principle?
“principal vs principle” is searched about 49,500 times a month on Google and 2,180 on Bing in the United States. Google counts close variants of a query together (“principle vs principal”, “principal or principle”).
Sources: Google Ads keyword data through DataForSEO and Microsoft Advertising keyword data through DataForSEO, the average month from September 2025 to August 2026.