principal and principle
These two words have the same pronunciation. The adjective principal means ‘main’, ‘most important’.
- What’s your principal reason for wanting to be a doctor? (not
… your principle reason …)
The noun principal means ‘head of a school’ (especially, in Britain, of a school for adults).
- If you want to leave early, you’ll have to ask the Principal.
A principle is a scientific law or a moral rule.
- Newton discovered the principle of universal gravitation. (not
… the principal of universal gravitation.) - She’s a girl with very strong principles.