principal

Etymology

From Middle English principal, from Old French principal, from Latin prīncipālis.

adj

1. Primary; most important; first level in importance.
   Smith is the principal architect of this design.
   The principal cause of the failure was poor planning.
   1760 [1726], Homer, tr. Alexander Pope, The Odyssey, Volume 2, page 217, In a word, the Epiſodes of Homer are complete Epiſodes; they are proper to the ſubject, because they are drawn from the ground of the fable; they are ſo joined to the principal action, that one is the neceſſary conſequence of the other, either truly or probably: and laſtly, they are imperfect members which do not make a complete and finiſhed body; for an Epiſode that makes a complete action, cannot be part of a principal action; as is eſſential to all Epiſodes.
   The principal treasure of ths department, however, is the Stele of Hammurabi (1792—1750 B.C.), king of the first Babylonian kingdom, a basalt cylinder 2.25m/7ft 5in. inscribed with Hammurabi′s laws written in Akkadian in cuneiform script. 1995, Madeleine Cabos, Baedeker Paris, page 105
   In theory, there are the same number of principal components as there are variables, but in practice, usually only a few of the principal components need to be identified to account for most of the data variance. 2005, Ruth N. Collins, “Application of Phylogenetic Algorithms to Assess Rab Functional Relationships”, in Sidney P. Colowick, Alan Hall, editors, Methods in Enzymology, volume 403, page 22
2. (obsolete, Latinism) Of or relating to a prince; princely.
3. (mathematics) Chosen or assumed among a branch of possible values of a multi-valued function so that the function is single-valued.
   Two is the principal square root of 4. Both −2 and +2 are square roots of 4.

noun

1. (finance, uncountable) The money originally invested or loaned, on which basis interest and returns are calculated.
   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. 1902, William Pember Reeves, State Experiments in Australia and New Zealand, volume 1, Cambridge University Press, published 2011, page 342
   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.
   If you know the principal amount, the interest rate, and the number of years the payments will be made, you can consult an amortization calculator or schedule to arrive at the monthly payment. 2012, Fred Steingold, Legal Forms for Starting & Running a Small Business, page 88
2. (Canada, US, Australia, New Zealand) The chief administrator of a school.
   The important administrative figure to the teacher is the school principal. 1971, Louis Kaplan, Education and Mental Health, page 413
   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.[…]’ 2008, Brian Dive, The Accountable Leader: Developing Effective Leadership Through Managerial Accountability, page 212
   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). 2009, Colin J. Marsh, Key Concepts for Understanding Curriculum, page 132
   2011, U.S. Department of Labor, Occupational Outlook Handbook 2011-2012, page 45, Principals are now being held more accountable for the performance of students and teachers, while at the same time they are required to adhere to a growing number of government regulations.
3. (UK, Canada) The chief executive and chief academic officer of a university or college.
   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
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.
   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. 1958, American Law Institute., Restatement of the Law, Second: Agency 2d, volume 7, page 533
   A food broker has been defined as an independent sales agent who performs the services of negotiating the sale of food and/or grocery products for and on account of the seller as principal. 1966, Pan American Union, The Marketing Structure for Selected Processed Food Products: In Sweden, Denmark, Norway, The Federal Republic of Germany, Canada and the United Kingdom, page 34
   2009, California Continuing Education of the Bar, California Probate Code, page 375, An attorney-in-fact has a duty to act solely in yhe interest of the principal and to avoid conflicts of interest.
5. (law) The primary participant in a crime.
   Coordinate term: accessory
   The accessories may be prosecuted, tried and punished, though the principal has not been prosecuted or has been acquitted. 1915, Eugene Allen Gilmore, Wiliam Charles Wermuth, Modern American Law, page 125
6. (Canada, US) A partner or owner of a business.
7. (music) A diapason, a type of organ stop on a pipe organ.
8. (architecture, engineering) The construction that gives shape and strength to a roof, generally a truss of timber or iron; or, loosely, the most important member of a piece of framing.
9. The first two long feathers of a hawk's wing.
   The first two feathers - Principals 1856, John Henry Walsh, Manual of British Rural Sports
10. One of the turrets or pinnacles of waxwork and tapers with which the posts and centre of a funeral hearse were formerly crowned
11. (obsolete) An essential point or rule; a principle.
    Set two classes of monitors to question each other; so that one may try to outquestion the other. Explain to them the principal of every subject they have to teach. 1847, Great Britain. Committee on Education, Minutes of the Committee of Council on Education, page 446
12. A dancer at the highest rank within a professional dance company, particularly a ballet company.
13. (computing) A security principal.