邮票有单枚的，也有十枚一册的。

The stamps are available singly or in books of ten.

《牛津词典》

英语中，名词有单复数之分。

In English, nouns can be singular or plural.

youdao

工作总结标题有单标题，也有双标题。

Summary of the work the title single title, also has the double title.

youdao

Like, I guess just sitting and watching The Simpsons, it's entertaining because they make jokes and they make us laugh.

我觉得如果单看《辛普森一家》,确实很有乐趣，因为它很搞笑，令人捧腹。

耶鲁公开课 - 公正课程节选

I just turned it on literally this morning to start playing and I'm on myself a couple of email lists, one of which had an email this morning saying, "Hey, has anyone tried this, it really kind of sucks."

今天早上我就碰到这样的情况了,我收到了两份邮件单，其中一份有一封邮件说，嗨，有人用过这个了吗，真是糟透了“

哈佛公开课 - 计算机科学课程节选

And orbiting around this is a lone electron out at some distance r.

有一个单电子,在环原子核的轨道上运行。

麻省理工公开课 - 固态化学导论课程节选