sundown vs sunset

sundown and sunset both are nouns.

Word	Noun	Adjective	Verb	Adverb
sundown	Yes	No	No	No
sunset	Yes	Yes	No	No

As nouns, sundown and sunset are synonyms defined as:

sundown and sunset: the time in the evening at which the sun begins to fall below the horizon

sundown (noun)	sunset (noun)
the time in the evening at which the sun begins to fall below the horizon	the daily event of the sun sinking below the horizon
	atmospheric phenomena accompanying the daily disappearance of the sun
	the time in the evening at which the sun begins to fall below the horizon

sundown (adjective)	sunset (adjective)
	providing for termination
	of a declining industry or technology