Principal /(?)/

Prin·ci·pal

Principal

Highest in rank, authority, character, importance, or degree; most considerable or important; chief; main; as, the principal officers of a Government; the principal men of a state; the principal productions of a country; the principal arguments in a case.
Wisdom is the principal thing.
— Prov. iv. 7.
Of or pertaining to a prince; princely. [A Latinism]

Principal axis: See Axis of a curve, under Axis.
Principal axes of a quadric: three lines in which the principal planes of the solid intersect two and two, as in an ellipsoid.
Principal challenge: See under Challenge.
Principal plane: See Plane of projection (a), under Plane.
Principal of a quadric: three planes each of which is at right angles to the other two, and bisects all chords of the quadric perpendicular to the plane, as in an ellipsoid.
Principal point: the projection of the point of sight upon the plane of projection.
Principal ray: the line drawn through the point of sight perpendicular to the perspective plane.
Principal section: a plane passing through the optical axis of a crystal.

A leader, chief, or head; one who takes the lead; one who acts independently, or who has controlling authority or influence; as, the principal of a faction, a school, a firm, etc.; -- distinguished from a subordinate, abettor, auxiliary, or assistant.
The chief actor in a crime, or an abettor who is present at it, -- as distinguished from an accessory. (Law)
A thing of chief or prime importance; something fundamental or especially conspicuous. (Com.) [Obs.]