principal and principle - the difference

The Quick Answer
Principal means main.
A principal is the head (of a department).
Principle means general law or code of conduct.

Writers occasionally confuse the words principal and principle.

Principal

In its most common role, principal is an adjective meaning main or key.

Examples:
  • The principal objective is to make a profit.
  • (The adjective principal modifies the noun objective.)
    (principal = main or key)
  • The inspector highlighted my principal concern in his opening sentence.
  • (principal = main or key)

The word principal can also be noun mean head or chief. It is commonly used to denote head teacher in the US.
  • Here comes the principal. 
  • (principal = head teacher)
  • The allegations against the former principal were that he not only allowed the cage fights to take place, but he also he egged on the participants.

Principle

The word principle is a noun. It has a range of meanings, including rule, belief, tenet and theory.  In general, principle offers the idea of general law or code of conduct.
  • No! It is against my principles!
  • That is a great idea in principle.
  • Those are my principles. If you don't like them, I have others. (Groucho Marx quote)
  • You could strengthen your argument by appealing to more general
    principles.
  • He applied the Aufbau principal to determine the electron configuration of the silicon.
  • (should be principle / principle = theory or general law)

See Also

adverse or averse? affect or effect? appraise or apprise? avenge or revenge? bare or bear? complement or compliment? dependant or dependent? discreet or discrete? disinterested or uninterested? e.g. or i.e.? envy or jealousy? imply or infer? its or it's? material or materiel? poisonous or venomous? practice or practise? tenant or tenet? who's or whose?
What are nouns? What are verbs? List of easily confused words