What is the meaning of principal?

noun

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

adjective

• Most important element.
  • usage: "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"
  • synonyms: chief, main, primary, master