principle-n; 4 Senses

Sense Number 1: a generalization

Commentary: A basic assumption that people use as a basis of reasoning or conduct. Not scientific.

John designed his room according to the principles of feng shui.
Your essay violates the basic principles of composition.
The principles of democracy grant power to the common people.

WordNet 2.0 Sense Numbers: 1 3

Sense Number 2: standard for behavior

Commentary: A general way of indicating morality or good behavior. Refers not to specific rules of conduct. Can be pluralized.

The American people want a President who stands by his principles.
He's a man of principle.
Our nation's moral principles are constantly falling apart.

WordNet 2.0 Sense Numbers: 2

Sense Number 3: scientific phenomena

Commentary: Refers to a law of the universe, to a scientific explanation of how something works.

In physics class, we learned the principle of conservation of momentum.
American scientists discovered the principles of the internal combustion engine.
John's plane used the principles of jet propulsion to achieve lift.

WordNet 2.0 Sense Numbers: 4 6

Sense Number 4: a specific rule of conduct

Commentary: Refers to a rule of conduct, not to morality in a general sense.

I've made it a personal principle never to seduce married women.
I follow seven principles of cooking meat products.

WordNet 2.0 Sense Numbers: 5