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B2

Principle vs Principal

Principle is a rule or fundamental idea — 'a matter of principle'. Principal is the head of a school (noun) or 'main/most important' (adjective) — the principal reason.

The one-line answer

Principle is a rule or fundamental idea — 'a matter of principle'. Principal is the head of a school (noun) or 'main/most important' (adjective) — the principal reason.

principle

noun

a fundamental rule, belief or truth — always a noun, never an adjective

  • She refused on principle.
  • The basic principles of physics apply here.
  • He's a man of strong principles.

principal

noun / adjective

noun: the head of a school or institution. Adjective: main, most important

  • The principal called an emergency meeting. (school head)
  • The principal reason for the delay was weather. (main)
  • She's the principal dancer of the company.

Memory trick

The principal is your 'pal' — a person at school. A principle is a rule — both end in '-le'. If you can replace it with 'main', use principal.

Principle vs Principal: Test yourself

Question 1 of 2

The ___ aim of the study was to reduce costs.