All 3 Uses of

principle
in
The Hot Zone

The tank worked on the same principle as a sliding cash drawer in a teller's window.†
p. 220.3 *

principle = basic rule or belief

Nancy herself had never worn a Racal field suit, but the principles are the same as with a heavy-duty Chemturion.†
p. 293.9

principles = basic rules or beliefs

The main principle is that the interior of the space suit is a cocoon housing the normal world, which you bring with you into the hot area.†
p. 294.0

principle = 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)
meaning too rare to warrant focus:

See a comprehensive dictionary for more specialized senses including one in chemistry.