sundown vs evening

sundown and evening both are nouns.

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

sundown (noun)	evening (noun)
the time in the evening at which the sun begins to fall below the horizon	the latter part of the day (the period of decreasing daylight from late afternoon until nightfall)
	a later concluding time period
	the early part of night (from dinner until bedtime) spent in a special way