Serene is deep, settled calm — the kind that looks like it would take something enormous to disturb. A serene lake, a serene smile, a serene expression at the end of a very bad week.
It is stronger and stiller than calm and warmer than composed. Calm can be temporary and can be an effort; serene suggests the state is natural and complete, which is why it suits water, skies, faces and old paintings, and sits oddly on a busy office. It is a written-register word: you would describe someone as serene, but you would rarely say it to them. The noun is serenity, and Your Serene Highness is a real royal address, which tells you how elevated the word once was.
1adjectivesereneDeeply calm and untroubled.
“She looked serene, which surprised everyone who knew the week she had had.”
synonyms: tranquil, peaceful, unruffled
2adjectivewaterOf water, sky or a scene: still and clear.
“The lake was serene at that hour, with nothing on it.”
serene is a state of calm.
Also accepted in games: tranquil
Latin serenus meant clear and cloudless, said of the sky and of the weather. The calm face came afterwards, by the obvious comparison: an untroubled person looks the way an untroubled sky does.
Latin
serēnus — clear, cloudless, untroubled
English, today
serene
From Middle English -, borrowed from Latin serēnus (“clear, cloudless, untroubled”).
Etymology from Wiktionary, CC BY-SA