11点30用英语表达是：half past eleven；

half ：n. 一半; 半; (比赛、音乐会等的)半场，半局; (啤酒等饮料的)半品脱。

past：adj. 过去的; 昔日的; 刚过去的; 刚结束的; 从前的; 以往的。

eleven：n. 十一; 十一个; 第十一十一。

I stayed awake on purpose until half past eleven.

我故意不睡觉熬到十一点半。

It's only half past eleven.

现在才十一点半。

At about half past eleven, when the floor began to shake under him.

大约十一点半左右，突然地板动了起来。

I stayed awake on purpose until half past eleven one evening in order to have a good look at the moon for once by myself.

有一天晚上，我熬到11点半故意不睡觉，为的是独自好好看看月亮一次。

It was now already half past eleven, but Tu Wei-yueh at the factory had not yet telephoned the expected news of victory.

钟上已经是十一点半了，预料中的屠维岳的告捷电话竟没来。