All 3 Uses

principle
in
Ordinary People
(Auto-generated)

To have a reason to get up in the morning, it is necessary to possess a guiding principle.†
p. 1.1

principle = basic rule or belief
There were one or two guiding principles to get him through the day.†
p. 5.8 *

principles = basic rules or beliefs
He had principles.†
p. 49.8

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.