principal definition

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