Denshi Jisho — Online Japanese dictionary

静か しずか quiet; peaceful
Common word, Na-adjective 
静か しずかに 1: calmly; quietly; gently; peacefully;
2: (Expression) be quiet!
Adverb 
静かに流れる川は深い しずかにながれるかわはふかい Still waters run deep
Expression, Idiomatic expression 

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