What does principle mean?
A principle is a basic rule, belief, or proposition that provides a foundation for thinking or acting. It may express an ethical commitment, as when someone acts on principle, or describe a governing idea in science, law, politics, art, or everyday organisation. The phrase “in principle” indicates that something is theoretically possible or appropriate, even if practical obstacles remain. Principles are often treated as stable and authoritative, giving the word a formal and sometimes moral tone. Although the meaning can overlap with “rule,” “tenet,” and “doctrine,” a principle often has a broader or more foundational force. The word can also refer to the essential character or constituent of something, as in the principle of least privilege in computing. Understanding principles helps identify the underlying ideas that guide systems, institutions, and individual decisions.
nounA fundamental rule, belief, or proposition that guides conduct, reasoning, or the operation of a system. The word can also refer to a person’s moral standards, as in someone described as having strong principles.
- A fundamental rule or belief that guides behaviour, conduct, or thought.
- A general law or proposition that explains how a system, process, or natural phenomenon works.
- A person’s moral standards or guiding ethical commitments.
- An essential constituent or fundamental quality of something.
"She refused the compromise on principle."
"The organisation operates on the principle that every member should have an equal voice."
"His decision to report the misconduct was a matter of principle."
The plural is common for a collection of guiding rules, beliefs, or ethical commitments, especially in political, legal, philosophical, and organisational contexts.
"The committee agreed that the proposal should be judged against these principles."
Principle comes from Latin principium, meaning “the first beginning”—an apt origin for the ideas that underpin everything else.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does principle come from?
The English word entered Middle English through Anglo-French and Old French forms from Latin principium, meaning “the first beginning,” “origin,” or “basis.” Latin principium developed from princeps, meaning “first” or “chief.” That same Roman root is reflected in English cognates including prince, princess, and principal, words that also refer to someone or something of leading importance.
Related word forms
How principle is actually used
The word is formal and abstract, especially when it refers to a moral rule or guiding belief. In general contexts, “principle” is countable and commonly used in the plural, as in “the principles of the agreement.”
Easily confused with principle
A principle is a rule, belief, or guiding idea, whereas a principal is a chief person or the leading member of a group; principal can also be an adjective meaning chief or most important.