politeness vs devoir

politeness and devoir both are nouns.

Word	Noun	Adjective	Verb	Adverb
politeness	Yes	No	No	No
devoir	Yes	No	No	No

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

Other hyponyms of politeness include courtesy, deference, respect.

politeness (noun)	devoir (noun)
the act of showing regard for others	formal expression of respect
a courteous manner that respects accepted social usage