principal principal /ˈprɪnsəpəl/

adjective

1. () Most important element  ( master , primary , chief , main , principal )
   most important element
    The chief aim of living
   the chief aim of living
    The main doors were of solid glass
   the main doors were of solid glass
    The principal rivers of America
   the principal rivers of America
    The principal example
   the principal example
    Policemen were primary targets
   policemen were primary targets
    The master bedroom
   the master bedroom
    A master switch
   a master switch
   

noun

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