/ səˈriːn; NAmE / adjective
calm and peaceful :
a lake, still and serene in the sunlight
► se·rene·ly adverb :
serenely beautiful
She smiled serenely.
► se·ren·ity / səˈrenəti; NAmE / noun [ U , sing. ]:
The hotel offers a haven of peace and serenity away from the bustle of the city.
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WORD ORIGIN
late Middle English (describing the weather or sky as clear, fine, and calm ): from Latin serenus .