principle /ˈprɪnsəpəl/ noun
plural principles
plural principles
Learner's definition of PRINCIPLE
: a moral rule or belief that helps you know what is right and wrong and that influences your actions
[count] : a basic truth or theory : an idea that forms the basis of something
[count] : a law or fact of nature that explains how something works or why something happens

in principle

used to say that something which has not yet happened or been done should be possible according to what is known
: in a general way and without giving attention to details
◊ Do not confuse principle with principal.