"平静"用英语可以表示为"calm"或"serene".

"Calm" 来源于拉丁语"calmus"，意为"静止的"或"平息的".

例句：

The weather was calm and clear. （天气平静晴朗。）

She spoke in a calm and reassuring voice. （她用一种平静且令人安心的声音说话。）

"Serene" 来源于拉丁语"serenus"，意为"清澈的"或"静谧的".

例句：

The lake was serene and still. （湖水平静无波。）

She maintained a serene demeanor throughout the difficult situation. （在困难的情况下，她保持着镇静的神态。）