平方公里在英语中被称为"square kilometer"。来源：这个单位来自古希腊，"平方"一词来源于拉丁语"quadrus"，意为"四边形"，"公里"则来源于希腊语"khilia"，意为"千"。

一些英文例句：

The park covers an area of more than 100 square kilometers.

The city has a population density of 1,500 people per square kilometer.

The wildfire burned through 5 square kilometers of forest.