Adjective

1. Primary; most important in a group.

   Smith is the principal architect of this design.

   The principal cause of the failure was poor planning.

Usage notes

• Not to be confused with principle.

This is generally not used in the comparative or superlative in formal writing, as the meaning is already superlative. However, one may occasionally see, e.g., more principal meaning more likely to be principal or more nearly principal. There are similar issues with unique.

The confused may care to remember that 'The principal alphabetic principle places A before E' as a reminder of the relative spelling.

Noun

1. The money originally invested or loaned, on which basis interest and returns are calculated

   A portion of your mortgage payment goes to reduce the principal, and the rest covers interest.

2. The principal administrator of a school

   Now you're in trouble! You're going to see the principal for that.

3. One who directs another (the agent) to act on one's behalf

   When an attorney represents a client, the client is the principal who permits the attorney, the client's agent, to act on the client's behalf.

4. A company represented by a sales person

   My principal sells metal shims

Adjective

1. main (principal)

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Etymology

principal, principalis

Adjective

1. principal, primary, chief, foremost