Calm
Serene, Tranquil
noun, な adjective
A place that is peace and quiet is a very calm and serene place. Ahh, so nice!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
こんなにカワイイ猫たちがいっぱいだと、平静を保てる自信がありません。
I am not sure I can keep my composure when so many cute cats are around.
私、好きな人の前では、平静でいられなくなるんです。
I find it hard to stay calm in front of someone I like.
彼女は赤信号で止まれずにパニックに落ちいっていたが、ラジオを聞きながら心の平静を取りもどした。
She was panicking, unable to stop at the red light, but regained her inner calm by listening to the radio.