principle · noun C /ˈprɪn.sə.pəl/Full view
principle (IDEA)
C1 a basic idea or rule that explains or controls how something happens or works
Dictionary examples:

the principles of law/ leadership/good government

Our science teachers created hands-on laboratories in which students can discover scientific principles.

The organization works on the principle that all members have the same rights.

Learner example:

Follow these two principles, [and] I'm sure you will become fit and healthy. (First Certificate in English; B2; Chinese)

on principle
C2 If you refuse to do something on principle, you refuse to do it because you think it is morally wrong.
Dictionary example:

She doesn't wear fur on principle.

Learner example:

They granted themselves a little celebration: it was time to keep the promise made four years before; so they bought some bottles of wine and got drunk (the[y] who, on principle, never drank alcohol). (Certificate of Proficiency in English; C2; Spanish)

in principle
C If you agree with something in principle, you agree with the idea or plan although you do not know the details or you do not know if it will be possible.
Dictionary example:

They have approved the changes in principle.

Learner example:

In principle, one can agree with both positions pointed out in this statement. (Certificate of Proficiency in English; C2; German)

principle (MORAL RULE)
C2 C or U a rule or belief which influences your behavior and which is based on what you think is right
Dictionary example:

He must be punished - it's a matter of principle.

Learner example:

He cheated every time he had the slightest opportunity to, even when it wasn't necessary at all. It was a matter of principle to him. (Certificate of Proficiency in English; C2; Greek)

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