Meaning & use
principle
Last updated
Meanings
nouncountable
A basic rule or belief about what is right that guides how a person behaves.
Grammar: Often plural when talking about someone's values: she has strong principles.
Patterns
- on principle
- a matter of principle
She refused the bribe because honesty was a matter of principle.
He has strict principles and never cheats.
I don't lie, as a principle.
nouncountable
A basic idea or rule that explains how something works or is done.
Grammar: Used for scientific and general rules; often followed by of.
Patterns
- the principle of something
- in principle
The machine works on the principle of leverage.
The teacher explained the principle of supply and demand.
They agreed to the plan in principle.
nouncountabletechnical
A general law or scientific truth that is accepted as foundational.
Grammar: Often found in names, such as the uncertainty principle.
Patterns
- the principle of something
Archimedes' principle explains why ships float.
The uncertainty principle is a basic idea in physics.
The first principle of the course is to ask questions.
Word forms
| plural | principles |
|---|
Common combinations
- moral principle
- Honesty is a moral principle she lived by.
- in principle
- In principle, I agree with the plan.
- on principle
- He refuses to cheat on principle.
- basic principle
- The basic principle is simple: be fair.
- stick to your principles
- She stuck to her principles even when it cost her.
- guiding principle
- Safety is the guiding principle of the project.
Synonyms and how they differ
- rule
- A rule is a specific instruction, whereas a principle is a broader idea behind it.
- belief
- A belief is something you hold to be true, but not necessarily a guide to behavior like a principle.
- ethic
- An ethic is a set of moral values, and is often used in the form work ethic.
- law
- A law, in the scientific sense, is a proven pattern, while a principle is more general and can be a guide.
Word family
- principled adjective
- acting according to strong moral beliefs
- unprincipled adjective
- lacking moral standards
- principally adverb
- mainly
- principal adjective
- most important
Commonly confused: principle or principal?
principle vs principal
Principal means main or the head of a school, but principle is a rule or belief. They sound the same.
Practice
She turned down the job offer on ____ because the company harmed the environment.
Choose one answer.
On principle means because of a moral belief. Principal means main or head of a school and does not fit.
Make it your own
Write a sentence using “principle”, then check it and compare it with the examples above.