11:30 in English can be said as "half past eleven" or "eleven thirty." These phrases are derived from the traditional way of telling time in which the hours and minutes are divided into halves and quarters.

Here are some example sentences using these phrases:

"I need to leave work at half past eleven today." (我今天11点半需要离开工作。)

"The movie starts at eleven thirty, so we should leave soon." (电影11点半开始，我们应该快点离开。)

"Can you meet me at half past eleven for lunch?" (你能11点半和我约饭吗？)