在英语中，"孤单"通常用单词"lonely"来表示。这个词的来源可以追溯到中世纪拉丁语单词"lone"，其本意是"单独的"或"与众不同的"。

一些英文例句和中文翻译如下：

I feel lonely when I'm home alone. (我一个人在家时感到孤单。)
She's always surrounded by friends, but she still feels lonely. (她总是被朋友包围着，但仍然感到孤单。)
He was lonely after his wife passed away. (他的妻子去世后感到孤单。)