Quiet
noun, な adjective
Leisurely quiet is the best kind of quiet. Even your brain gets to be quiet because you don't have a care left in the world.
かんせい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
この辺りは、閑静な住宅街になっています。
This neighborhood is now a quiet residential area.