principal

1. (finance, uncountable) The money originally invested or loaned, on which basis interest and returns are calculated.Examples: "A portion of your mortgage payment goes to reduce the principal, and the rest covers interest."; "In March 1902, I find in the statement of liabilities and assets £711 put down as arrears of interest, but there is no entry of arrears of principal."; "2012, Denis Clifford, Plan Your Estate, 11th Edition, NOLO, US, page 298, For instance, in some states, dividends that have automatically been reinvested will be treated as principal."uncountable

2. (Canada, US, Australia, New Zealand, Philippines) The chief administrator of a school.Examples: "The important administrative figure to the teacher is the school principal."; "The problem was neatly summed up by one principal in Australia who said recently: ‘There is no incentive for me to develop my best teachers to become my successor.[…]’"; "Now renamed Teaching Australia, its officers are undertaking exploratory steps in developing professional standards for school leaders. A National Standards Drafting Group of volunteer principals is currently drafting principal standards (Teaching Australia, 2007)."Synonyms: headteacher, headmaster, headmistressAustraliaCanadaNew-ZealandPhilippinesUScountableuncountable

3. (UK, Canada) The chief executive and chief academic officer of a university or college.Examples: "1967, University of Edinburgh Graduates′ Association, University of Edinburgh Journal, Volumes 23-24, page 314, Unlike the students, Principal Robertson, who now resided almost alone in the College, continued to use the accustomed route on his visits to the Old Town; and it “became the joke of the day that from being the principal gate it had become only a gate for the Principal.”⁵"; "Coordinate term: bursar"Synonyms: dean, rectorCanadaUKcountableuncountable

4. (law) A legal person that authorizes another (the agent) to act on their behalf; or on whose behalf an agent or gestor in a negotiorum gestio acts.Examples: "When an attorney represents a client, the client is the principal who permits the attorney, the client′s agent, to act on the client′s behalf."; "My principal sells metal shims."; "The firm admitted the amount owed, but averred as an affirmative defense that it had hired the expert as an agent of a disclosed principal, the client."Synonyms: clientcountableuncountable

5. (law) The primary participant in a crime.Examples: "The accessories may be prosecuted, tried and punished, though the principal has not been prosecuted or has been acquitted."Synonyms: ringleadercountableuncountable

6. (Canada, US) A partner or owner of a business.Synonyms: proprietorCanadaUScountableuncountable