refusal vs declination

refusal and declination both are nouns.

Word	Noun	Adjective	Verb	Adverb
refusal	Yes	No	No	No
declination	Yes	No	No	No

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

Other hyponyms of refusal include regrets.

refusal (noun)	declination (noun)
a message refusing to accept something that is offered	a polite refusal of an invitation
the act of refusing	(astronomy) the angular distance of a celestial body north or to the south of the celestial equator; expressed in degrees; used with right ascension to specify positions on the celestial sphere
	a downward slope or bend
	a condition inferior to an earlier condition; a gradual falling off from a better state; decline