first or highest in rank, importance, value, etc.; chief; foremost.

of, of the nature of, or constituting principal or capital

a principal investment.

Geometry . (of an axis of a conic) passing through the foci.

a chief or head.

the head or director of a school or, esp. in England, a college.

a person who takes a leading part in any activity, as a play; chief actor or doer.

the first player of a division of instruments in an orchestra (excepting the leader of the first violins).

something of principal or chief importance.

Law .

a person who authorizes another, as an agent, to represent him or her.

a person directly responsible for a crime, either as an actual perpetrator or as an abettor present at its commission. Compare accessory ( def. 3 ) .

a person primarily liable for an obligation, in contrast with an endorser, or the like.

the main body of an estate, or the like, as distinguished from income.

Finance . a capital sum, as distinguished from interest or profit.

Music .

an organ stop.

the subject of a fugue.

(in a framed structure) a member, as a truss, upon which adjacent or similar members depend for support or reinforcement.

each of the combatants in a duel, as distinguished from the seconds.

adjective

auxiliary , extra , least , lesser , minor , secondary , trivial , unimportant

noun

interest

adjective

arch , capital , cardinal , champion , chief , controlling , crowning , dominant , essential , first , foremost , greatest , head , highest , incomparable , key , leading , main , mainline , major , matchless , maximum , outstanding , paramount , peerless , predominant , preeminent , premier , prevailing , primary , prime , prominent , second-to-none , sovereign , star , stellar , strongest , supereminent , superior , supreme , transcendent , unapproachable , unequaled , unparalleled , unrivalednotes:principle means fundamental , as in beliefs or truths or understandings and it is always a noun; principal can be a noun or adjective meaning chief or of first importance , number one , top

noun

administrator , boss , chief , dean , director , exec , head , key player , lead , leader , preceptor , protagonist , rector , ruler , star , superintendentnotes:principle means fundamental , as in beliefs or truths or understandings and it is always a noun; principal can be a noun or adjective meaning chief or of first importance , assets , capital , capital funds , moneynotes:principle means fundamental , arch , cardinal , champion , dominant , essential , first , foremost , headmaster , high , highest , important , main , money , outstanding , paramount , predominant , preeminent , preponderant , primal , primary , prime , stellar