principal in WordNet English dictionary

1. most important element
   "the chief aim of living"; "the main doors were of solid glass"; "the principal rivers of America"; "the principal example"; "policemen were primary targets"; "the master bedroom"; "a master switch"
   chief  main  primary  principal  master 
   

1. capital as contrasted with the income derived from it
   principal  corpus  principal sum 
   
2. the major party to a financial transaction at a stock exchange; buys and sells for his own account
   principal  dealer 
   
3. the educator who has executive authority for a school
   "she sent unruly pupils to see the principal"
   principal  school principal  head teacher  head 
   
4. an actor who plays a principal role
   star  principal  lead 
   
5. (criminal law) any person involved in a criminal offense, regardless of whether the person profits from such involvement
   principal 
   
6. the original amount of a debt on which interest is calculated
   principal