adj. & n.
1. (usu. attrib.) first in rank or importance; chief (the principal town of the district).
2 main, leading (a principal cause of my success).
3 (of money) constituting the original sum invested or lent.
1. a head, ruler, or superior.
2 the head of some schools, colleges, and universities.
3 the leading performer in a concert, play, etc.
4 a capital sum as distinguished from interest or income.
5 a person for whom another acts as agent etc.
6 (in the UK) a civil servant of the grade below Secretary.
7 the person actually responsible for a crime.
8 a person for whom another is surety.
9 each of the combatants in a duel.
10 a a main rafter supporting purlins. b a main girder.
11 an organ stop sounding an octave above the diapason.
12 Mus. the leading player in each section of an orchestra.
Phrases and idioms:
principal boy (or girl) an actress who takes the leading male (or female) part in a pantomime. principal clause Gram. a clause to which another clause is subordinate. principal in the first degree a person directly responsible for a crime as its actual perpetrator. principal in the second degree a person directly responsible for a crime as aiding in its perpetration. principal parts Gram. the parts of a verb from which all other parts can be deduced.
Etymology: ME f. OF f. L principalis first, original (as PRINCE)