Principle vs. Principal

The words principle and principal are pronounced in the same way but they do not have the same meaning.

A Principle is a noun. Its main meaning is 'a fundamental idea or general rule that is used as a basis for a particular theory or system of belief'.

E. g.

This is one of the basic principles of democracy.

The directive principles of state policy.

Principal , on the other hand, is normally an adjective meaning 'main or most important'.

E. g.

One of the country's principal cities.

Principal can also be a noun, where it is used to refer to the most senior or most important person in an organization or of another group.

E. g.

She is the Principal of the school.