��天是 "today"，昨天是 "yesterday"。

这两个词都来自于古英语。"Today" 源自于古英语 "tō dæg"，意思是 "这一天"，"yesterday" 源自于古英语 "geostran dæg"，意思是 "前一天"。

以下是一些英文例句及其中文翻译：

I will see you today. (我今天会见到你。)
Yesterday was a really hot day. (昨天是一个非常热的一天。)
I didn't see you yesterday. (我昨天没有见到你。)
Today is Friday. (今天是星期五。)
Yesterday was Thursday. (昨天是星期四。)