in touch 联系，接触；了解

Let's keep in touch.

咱们保持联系吧。

I'll be in touch again towards the end of the week.

我到周末时再联系。

I try to keep in touch with current events by reading the newspapers.

我通过读报来尽量了解时事。

in turn 依次，轮流；转而

The girls called out their names in turn.

那些女孩儿逐一报出自己的名字。

They answered the teacher's questions in turn.

他们依次回答了老师的问题。

The students clean the classroom everyday in turn.

学生们每天轮流打扫教室。

in vain 徒劳，白费力

All our work was in vain.

我们的工作全都白干了。

Day after day she waited in vain for him to telephone her.

日复一日，她徒劳地等待他的电话。

We tried in vain to make him change his mind.

我们想使他改变主意，结果是白费心思。