- A basic truth, law, or assumption: the principles of democracy.
- A rule or standard, especially of good behavior: a man of principle.
- The collectivity of moral or ethical standards or judgments: a decision based on principle rather than expediency.
- A fixed or predetermined policy or mode of action.
- A basic or essential quality or element determining intrinsic nature or characteristic behavior: the principle of self-preservation.
- A rule or law concerning the functioning of natural phenomena or mechanical processes: the principle of jet propulsion.
- Chemistry One of the elements that compose a substance, especially one that gives some special quality or effect.
- A basic source. See Usage Note at principal.
- in principle With regard to the basics: an idea that is acceptable in principle.
- on principle According to or because of principle.