principle vs scruple

principle and scruple both are nouns.

Word	Noun	Adjective	Verb	Adverb
principle	Yes	No	No	No
scruple	Yes	No	Yes	No

As nouns, scruple is a hyponym of principle; that is, scruple is a word with a more specific, narrower meaning than principle:

principle (noun)	scruple (noun)
a basic truth or law or assumption	an ethical or moral principle that inhibits action
a rule or standard especially of good behavior	uneasiness about the fitness of an action (particularly for reasons of ethics, morals or propriety)
(law) an explanation of the fundamental reasons (especially an explanation of the working of some device in terms of laws of nature)	a unit of apothecary weight equal to 20 grains
a basic generalization that is accepted as true and that can be used as a basis for reasoning or conduct
a rule or law concerning a natural phenomenon or the function of a complex system
rule of personal conduct