1 truth, given, precept, tenet, fundamental, grounds, law, rule, dictum, canon, doctrine, teaching, dogma, proposition, (basic) assumption, postulate, axiom, maxim, truism, guide, standard, criterion, model:
The perpetual-motion machine violates a basic principle of physics.
2 Often, principles. philosophy, code, attitude, (point of) view, viewpoint, sentiment, belief, credo, creed, idea, notion, ethic, sense of right and wrong:
He cynically conducts his life on the principle, 'Do unto others before they do unto you'. I am not sure I can condone his principles
3 (sense of) honour, uprightness, honesty, morality, morals, probity, integrity, conscience:
If you don't think him a man of principle, don't do business with him
4 in principle. on principle, in theory, theoretically, basically, fundamentally, at bottom, in essence, essentially, ideally:
I like your plan in principle, but in practice it cannot be accomplished that way.