Serene means calm, peaceful, and tranquil. It implies a state of complete composure and absence of worry, stress, or disturbance.

Here are some synonyms for serene:

* Tranquil

* Peaceful

* Calm

* Quiet

* Composed

* Placid

* Unruffled

* Still

* Gentle

* Relaxed

Examples:

* "The serene lake reflected the clear blue sky."

* "She had a serene smile on her face."

* "The serene atmosphere of the meditation room helped me to relax."

Origin:

The word "serene" comes from the Latin word "serēnus," meaning "clear, bright, calm."