serene

 
Pronunciation: /sɪˈriːn/

adjective

  • calm, peaceful, and untroubled; tranquil: her eyes were closed and she looked very serene serene certainty

noun

(usually the serene) archaic
  • an expanse of clear sky or calm sea: not a cloud obscured the deep serene

Derivatives

serenely

adverb

Origin:

late Middle English (describing the weather or sky as 'clear, fine, and calm'): from Latin serenus