principal

First or highest in rank or importance. synonym: chief.

Of, relating to, or being financial principal, or a principal in a financial transaction.

One who holds a position of presiding rank, especially the head of an elementary school, middle school, or high school.

A main participant in a situation, especially a financial transaction.

A person having a leading or starring role in a performance, such as the first player in a section of an orchestra.

An amount of capital originally borrowed or invested, as opposed to the interest paid or accruing on it.

The most significant part of an estate, as opposed to minor or incidental components.