Sunset
Part of speech: noun
Definition: The time of day when the sun disappears below the western horizon. The changes in color of the sky at sunset. The final period of the life of a person or thing. (attributively) Of or relating to the final period of the life of a person or thing. (attributively) Having a set termination date.
Example sentence: All architecture is great architecture after sunset; perhaps architecture is really a nocturnal art, like the art of fireworks.
Sundown
Part of speech: noun
Definition: sunset