な adjective
しずか
静かな通りにある家の方がいいです。
We'd prefer a house on a quiet street.
下りなのは分かりますが、もう少し静かにしていただけますか？
I know you have diarrhea, but could you keep it down a bit more, please?
コウイチとビエトが乗り込むと、そのタクシーは静かに動き出した。
When Koichi and Viet got in, the taxi quietly started to move.
This is the な adjective form of quiet, which is kind of just like the noun, anyways. What is the adjective version of quiet? It's also quiet.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you: You need to be quiet. She's (しず) being nice and quiet, unlike you!