All 3 Uses of

principal
in
The Sunlight Dialogues

You just keep up the interest, they said, don't you worry about the principal.†
Chpt 1 *

principal = most important; or person that is most important

He called the nurse in to hear it, but Boyle would perform no more, could only smile as he'd done (he remembered suddenly and vividly) in grade school when Mrs. Wheat called the Principal to hear him.†
Chpt 2

She understood, too, his restless arrogance, the disgust he felt for teachers, principals, Education professors at the university, parents who were riding high in the world, who spoke kindly, condescendingly to him as though his fallen condition were of course a punishment for sins.†
Chpt 5

principals = most important; or people that are most important

Definitions:

(1) (principal)
most important; or person who is most important
The exact meaning of principal can depend upon its context. For example:
- "the principal idea" or "the principal performer" -- the most important
- "the principal of the school" -- the person in charge
- "a principal of a company" -- an owner or person with controlling authority
- "the principal in a transaction" (as contrasted to the agent) -- the person on whose behalf an agent acts
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

See a comprehensive dictionary for specialized senses in finance, architecture, law, chemistry, and music.