sign作“迹象、征兆”解时是可数名词。在表达“没有……迹象”时既可以说成show no sign/signs of，亦即sign用单复数均可;并且它既可作及物动词，也可作不及物动词。

如表达“警察以手势示意我们停车”有以下三种说法：

1. The policeman signed us to shop.

2. The policeman signed to us to stop.

3. The policeman signed for us to stop.