calmly; quietly; gently; peacefully
Adverbial form of 静か, used to describe doing something in a calm, quiet, or gentle manner.
彼は静かにドアを閉めた。
He quietly closed the door.
赤ちゃんが静かに眠っている。
The baby is sleeping peacefully.
Used as an imperative expression to tell someone to be quiet or calm down.
静かに！今、大事な話をしているんだ。
Be quiet! I'm talking about something important right now.
Adverbial form of the na-adjective 静か (shizuka), which is of native Japanese origin. The exact derivation of 静か is uncertain.