All 4 Uses

principle
in
The Princess Diaries
(Auto-generated)

She's always said that when sovereignty is vested in a single person whose right to rule is hereditary, the principles of social equality and respect for the individual within a community are irrevocably lost.†
Chpt 2 *

principles = basic rules or beliefs
But Lilly says it's the principle of the thing, and that maybe if people had made a big deal about how the Nazis smashed up Jewish people's store windows on Kristalnacht they wouldn't have ended up putting so many people in ovens.†
Chpt 3

principle = basic rule or belief
I also respect her because she is deeply principled: She says she would never think of inflicting her beliefs on others and would thank others to pay her the same courtesy.†
Chpt 3

principled = with or based on basic beliefs
Michael really didn't have anyone else to hang out with, since Principal Gupta ruled that the Internet is not a culture and therefore cannot have its own table, and so the Computer Club boycotted the Cultural Diversity Dance on principle.†
Chpt 5

on principle = because of a basic rule or belief

Definitions:

(1) (principle)
a basic rule or belief
The exact meaning of principle can depend upon its context. For example:
- "our guiding principles" -- basic moral beliefs that guide decisions and behavior
- "electromagnetic principles" -- rules describing how the world works
- "She lacks principles." -- lacks moral guidelines
- "We agree in principle." -- about important basic beliefs
(2) (meaning too rare to warrant focus)
See a comprehensive dictionary for more specialized senses including one in chemistry.