principal

Primary; most important; first level in importance.

Smith is the principal architect of this design.

The principal cause of the failure was poor planning.

Of or relating to a prince; princely.

But walkt at will, and wandred to and fro, / In the pride of his freedome principall.

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.

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.

The chief administrator of a school.

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.[…]’

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

Coordinate term: bursar

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 primary participant in a crime.

The accessories may be prosecuted, tried and punished, though the principal has not been prosecuted or has been acquitted.