Prin'çi-pal1, a.
a. [Lat. principālis, Fr., Pr., Sp., & Pg. principal, It. principale. See PRINCE.] 1. Highest in rank, authority, character, or importance; most considerable; chief; as, the principal officers of a government; the principal men of a city, town, or state; the principal arguments in a case; the principal beams of a building; the principal productions of a country. Wisdom is the principal thing. Prov. iv. 7. 2. Pertaining to a prince; princely. [A Latinism.] [Obs.] “In the pride of his freedom principal.” Spenser. Principal axis (Conic Sections), the axis which passes through the two foci; in the parabola, the diameter passing through the focus. Math. Dict.—Principal challenge (Law), a challenge of a juror for a cause which carries with it, prima facie, evident marks of suspicion, either of malice or favor. Burrill.—Principal point (Persp.), the projection of the point of sight upon the plane of projection; the center of the picture. Math. Dict.—Principal ray (Persp.), the line drawn through the point of sight perpendicular to the perspective plane. Math. Dict.—Principal section (Crystallog.), a plane passing through the optical axis of a crystal.