Principle
Etymology
From Latin "principium" (a beginning, origin, foundation), from "princeps" (first, chief, leader), itself "primus" (first) plus a root of "capere" (to take) — "the one who takes first place." A principle is thus, literally, a starting point or first thing: the foundation from which the rest is derived, whether in ethics or in physics.
noun · /PRIN-suh-puhl/
A fundamental rule or standard that guides conduct or reasoning.
What it names
Reach for it to name a general commitment you hold in advance and apply consistently — the fixed point from which specific decisions follow.
Example
He turned down the lucrative contract on principle, unwilling to work for a client he’d exposed.
Related idea
A value is something you care about; a principle is the rule that translates that value into a consistent standard of action. Acting "on principle" means letting the general rule override the tempting particular — the opposite of expedience.
noun · /PRIN-suh-puhl/
A fundamental natural law, or the basic way a device works.
What it names
a governing law of nature or operation
Example
Archimedes’ principle explains why ships float; the engine works on the principle of internal combustion.
Related idea
Not a rule of conduct but a rule of how things behave. Compare theory.