过期的英语是 "expired"。这个词来源于拉丁语 "exspirare"，意思是 "吐气，呼气"，后来引申为 "终止，结束"。

例句：

This milk has expired. It has a sour smell. 这牛奶已经过期了。它有一股酸味。
The pcense for this software has expired. You need to renew it in order to continue using it. 这个软件的许可证已经过期。你需要续订它才能继续使用。
The expiration date on this prescription is from 10 years ago. You need to get a new one from your doctor. 这张处方的有效期是10年前的。你需要向医生开一张新的。