Principle
noun
Definition
1. (noun) A basic belief or rule that guides how you behave and what you think is right or wrong.
2. (noun) A fundamental truth, law, or idea that forms the basis of how something works or is understood.
2. (noun) A fundamental truth, law, or idea that forms the basis of how something works or is understood.
Context Alive
Your boss asks you to lie to a client about a delivery date so the company does not lose the deal. You know it would make your life easier, but you refuse because honesty is a principle you are not willing to bend on. Your boss looks annoyed but drops it. Later that week the client finds out the real timeline and thanks you for being straight with them. Sometimes sticking to your principles costs you in the short term but pays off later.
Meanings
2 meanings 1 A Personal Belief About Right and Wrong (Noun) Very Common ▼
This meaning is about the moral rules you live by — the things you believe in strongly enough to follow even when it is difficult. Imagine a journalist who refuses to reveal a source even when pressured by the police — protecting sources is a principle she will not compromise on. This is describing a deep personal belief that shapes your decisions and behaviour. You might hear "he is a man of principle who always keeps his word", or someone could say "I won't do it — it's against my principles" when asked to do something dishonest. Or picture a politician who votes against her own party because the policy conflicts with her core principles. The word suggests something you hold onto regardless of convenience or pressure.
✏️ Principle and principal sound identical but mean completely different things. Principle = a belief or rule. Principal = the head of a school, or "main/chief" as an adjective. This is one of the most confused word pairs in English. A quick trick: principle ends in -le like "rule," and it means a rule you live by.
2 A Fundamental Law or Idea (Noun) Very Common ▼
This meaning is about a basic truth or concept that explains how something works — in science, philosophy, economics, or any field. Imagine a physics teacher explaining that gravity pulls everything toward the centre of the Earth — this is one of the fundamental principles of physics. This is describing a foundational idea that other things are built upon. You might read "the principle of supply and demand" in an economics textbook, or someone could say "the design follows the principle that less is more" about a minimalist building. Or think about a lawyer explaining that everyone is innocent until proven guilty — a core principle of the legal system. The word suggests something basic, foundational, and widely accepted.
✏️ In this sense, principle is often used with "of" — "the principle of..." followed by the concept. Common phrases include "basic principles," "first principles," "guiding principles," and "the principle behind something." In business, companies often publish their "core principles" or "founding principles" to explain what they stand for. Scientists use the word constantly: "the principle of relativity," "the uncertainty principle."
Common Patterns
Moral/Ethical Use
a matter of principle → something you do because of your beliefs, not for practical reasons
She refused the bribe — it was a matter of principle.
against someone's principles → something that conflicts with a person's core beliefs
Lying is against his principles, even when the truth is uncomfortable.
a man / woman of principle → someone known for having strong moral standards
He is a man of principle and everyone in the office respects him for it.
Fundamental Law/Idea
the principle of + noun → the foundational concept behind something
The principle of equal opportunity is central to modern employment law.
basic / fundamental principles → the most important underlying ideas of a subject
The course covers the basic principles of economics.
in principle → as a general idea, even if the details are not yet agreed
We agreed in principle, but the contract still needs to be finalised.
Collocations
10 collocationsbasic principles
the most fundamental rules or ideas of a subject
guiding principle
a belief that directs decisions and actions
core principles
the most important values of a person or organisation
matter of principle
an issue decided by beliefs rather than convenience
against one's principles
in conflict with someone's personal moral rules
first principles
the most basic concepts from which everything else is built
in principle
as a general concept, even if not yet in practice
moral principles
beliefs about what is right and wrong
the principle behind
the fundamental idea that explains how something works
on principle
because of your beliefs, not for any other reason
Example Sentences
10 examples
1
She refused to cheat on the exam — it was against her principles.
She would not cheat on the test because it went against her personal moral standards.
2
The company was founded on the principle that everyone deserves access to clean water.
The business was built around the belief that clean water should be available to all.
3
He agreed in principle but said he needed to see the full proposal before signing.
He accepted the general idea but wanted to read the complete plan before committing.
4
The course teaches the basic principles of graphic design to complete beginners.
The programme covers the fundamental concepts of visual design for people with no experience.
5
It was a matter of principle — he would not accept money he had not earned.
It was about his beliefs — he refused to take payment for work he had not done.
6
She is a woman of strong principles and never compromises on what she believes is right.
She has firm moral values and refuses to bend on what she considers fair and honest.
7
The principle of supply and demand is one of the first things you learn in economics.
The concept that prices rise when supply drops and demand grows is a basic lesson in economics.
8
He donated his bonus to charity on principle because he felt his team deserved it more.
He gave his bonus away because he believed his colleagues had earned it, not him.
9
The legal system is built on the principle that everyone is innocent until proven guilty.
The justice system is based on the idea that nobody is treated as a criminal until a court confirms it.
10
Understanding the principles behind the technology will help you use it more effectively.
Knowing the basic ideas that make the technology work will help you get more out of it.
Synonyms & Antonyms
6 items
Synonymsvalue
more personal and emotional — what matters to you as a person
belief
broader — covers moral, religious, and personal convictions
rule
more practical and concrete — something you follow, not just believe in
Antonymscorruption
the absence of moral principles — acting dishonestly for personal gain
hypocrisy
claiming to have principles but not actually following them
compromise
giving up part of what you believe in for practical reasons