principle

A belief about right and wrong that guides how you behave.

• Honesty is an important principle for me.
• She refused the money on principle.
• Would you break your principles to help a friend?

How to use it: on principle (He refuses to buy stolen goods on principle.); against someone’s principles (Lying to customers is against my principles.)

Similar words: belief, value

Common phrases: moral principle, matter of principle, principle of honesty, a firm principle

A basic rule or idea that explains how something works.

• The machine works on a simple principle.
• We studied the principles of flight.
• Can you explain the principle behind this design?

How to use it: principle behind something (The principle behind the pump is easy to understand.); principle of something (We learned the principle of heat transfer.)

Similar words: rule, law

Common phrases: basic principle, scientific principle, principle of something

A basic belief, rule, or starting idea on which other ideas or decisions depend.

• Equality is a guiding principle of our organization.
• Their argument rests on two basic principles.
• We agreed on the principle that everyone should have a voice.

How to use it: principle that + clause (We accept the principle that all votes have equal value.)

Similar words: foundation, tenet

Common phrases: guiding principle, fundamental principle, principle of equality