More poetic than "sunset". Compare "twilight" (which covers both dawn and dusk).
1the darker stage of twilight, just before night
We arrived at dusk.
"At the dawn of" = at the beginning of (used metaphorically: "the dawn of a new era"). "From dawn till dusk" = all day long.
2the first appearance of light in the sky before sunrise
They set out at dawn.
"The Twilight Zone" was a famous TV series. The "Twilight" book/film series popularized the word with vampires.
the soft glowing light in the sky between full daylight and complete darkness
They walked along the beach at twilight.
(figurative) a period in which something is gradually declining
He's in the twilight of his career.
= 12:00 a.m. Contrast 'noon' (12:00 p.m.). 'Burn the midnight oil' = work late into the night.
twelve o'clock at night; the middle of the night
The shops stay open until midnight on Fridays.
the middle of the day; noon
He awoke at midday.
"Good night" as a farewell, not a greeting. Idioms: "night and day" = constantly, "a night owl" = someone who stays up late, "call it a night" = stop for the day.
the period of darkness between sunset and sunrise
They drove through the night to reach the coast.
"Good evening" as a greeting, used from late afternoon/dusk until bedtime. "Evening gown": formal dress for evening events.
the period of the day between afternoon and night
They went for a walk in the evening.
"Good afternoon" as a greeting, used roughly noon-6pm. British: "afternoon tea" is a light meal, distinct from "high tea" (evening meal).
the period of the day between noon and evening
We spent the afternoon at the museum.
Synonym: midday (different root; from Latin nona hora, "ninth hour"). "High noon": exactly midday, or a moment of decisive confrontation (from the 1952 film).
twelve o'clock in the middle of the day
The meeting is scheduled for noon.
"Good morning" as a greeting. "Morning sickness": nausea in early pregnancy. "Morning-after pill".
the early part of the day, from sunrise (or midnight) until noon
She goes for a run every morning.
Opposite: sunset. More visual/concrete than "dawn", which emphasizes the first light rather than the sun's disk appearing.
1the time when the sun rises above the horizon in the morning
We woke up early to watch the sunrise.
Opposite: sunrise. "Sunset years/clause" = figurative use for a final or expiring period.
2the time when the sun disappears below the horizon in the evening
They watched the sunset from the pier.