He signaled (to) the waiter to bring the menu.

他示意服务员把菜单拿过来。

常用结构：

signal to sb./sth. for sth.

用信号传达（某信息）；用信号与（某人）通讯

signal with ...用......发信号

高手过招

翻译句子

①铁路的红信号灯亮了，所以火车停下了。

②他用红旗传达信号。

答案：①The railway signal was on red, so the train stopped.

②He was signalling with a red flag.

3. sum

n. 金额; 款项; 总数; 算术题

常用结构：

in sum 简言之; 总而言之

sum up/sum sth. Up 总结；概括

He was fined the sum of 200$. 他被处以200美元的罚金。

The sum of 5 and 3 is 8. 5加3的和是8。

To sum up, there are three main ways of solving the problem.

概括起来说，这个问题主要有三种解决办法。