the chief and most necessary part of a thing. The principal of a college or hall is the master thereof. In commerce, principal is the capital of a sum due or lent, and is so called in opposition to interest. It also denotes the first fund put by partners into a common stock, by which it is distinguished from the calls or accessions afterwards required.

in Music, see Organ. The term principal is also used in music to designate the more distinguished part written for an instrument where there are several parts written in harmony, and where one of these parts is intended to be the chief and most conspicuous; as in a violin concerto, Violino Principale, and so of other instruments.