remark vs courtesy

remark and courtesy both are nouns.

Word	Noun	Adjective	Verb	Adverb
remark	Yes	No	Yes	No
courtesy	Yes	No	No	No

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

remark: a statement that expresses a personal opinion or belief or adds information
courtesy: a courteous or respectful or considerate remark

remark (noun)	courtesy (noun)
explicit notice	a courteous or respectful or considerate act
a statement that expresses a personal opinion or belief or adds information	a courteous manner
	a courteous or respectful or considerate remark

remark (verb)	courtesy (verb)
make mention of
make or write a comment on