IPA: /səˈriːnəs/
KK: /səˈrinəs/
The quality of being calm, peaceful, and untroubled.
The serene lake reflected the clear blue sky, creating a sense of calmness.
Sereneness is formed from "serene" (from Latin "serenus", meaning clear, calm, or tranquil) and the suffix "-ness" (meaning the state or quality of). The word describes the state of being calm and peaceful.
Think of the word 'serene' which means calm and peaceful, and remember that 'sereneness' refers to the quality of being serene.