›[C]a basic idea or rule that explains or controls how something happens or works: a principle of sthThose who paid the most would be earning the most: it's a pretty basic principle of fair taxation.basic/fundamental/general principleThe general principles of project management are much the same in the two cases.on the principle thatThe organization works on the principle that all members have the same rights. The country is run on socialist principles.
›[C or U]a moral rule or standard of good behaviour: I never cheat a customer, as a matter of principle.She'd never ask to borrow money, on principle.
in principle›if you agree with or believe something in principle, you agree with the idea in general, although you might not agree with all the details or support it in every situation: In principle, we support the merger, but we think the value is insufficient.The EU may also move to implement a ban on new investment, previously agreed in principle.›if something should happen in principle, it should happen in theory although it does not in fact always happen or has not yet happened: In principle, bonuses ought to fall when conditions get tough. In practice, they don't.