Meaning : Not agitated. Without losing self-possession.
Example :
Spoke in a calm voice.
Remained calm throughout the uproar.
He remained serene in the midst of turbulence.
A serene expression on her face.
She became more tranquil.
Tranquil life in the country.
Synonyms : calm, tranquil, unagitated
Meaning : Completely clear and fine.
Example :
Serene skies and a bright blue sea.