a pair of后所接名词主要有以下特点：

1. 由两部分构成的单件事物，如trousers(裤子)，scissors(剪刀)，glasses(眼镜)

spectacles(一副眼镜)，jeans(牛仔裤)等。如：

I cut the paper with a pair of scissors. 我用剪刀剪纸。

Two pairs of your trousers are still at the cleaner’s. 你的两条裤子还在洗衣店里。

对于这类由两部分构成的单件事物，我们不能用one或ones来替代它，而用pair或pairs。如：

这些裤子我穿太紧了，你有宽一点的吗?

误：These trousers are too tight for me. Do you have a larger one?

正：These trousers are too tight for me. Do you have a larger pair?

2. 包括两件东西并且习惯上一起使用的名词，如shoes(鞋子)，boots(靴子)sgloves(手套)，socks(袜子)，earrings(耳环)，chopsticks(筷子)等。如：

A pair of gloves is a nice present. 一付手套是一件很好的礼物。

Go and buy yourself a new pair of shoes. 去给自己买双新鞋吧。

I want to buy a hat and a pair of boots, among other things. 除别的东西之外，我还想买顶帽子和一双皮靴。

3. 表示身体中两个相同的部位。如：

She has a huge pair of eyes. 她长有一双大眼睛。

Look at her beautiful pair of legs. 你瞧她那又美丽的大腿。

4. 表示一般意义的“两个”“一对”等。如：

On the wall were a pair of hearts interlocked. 墙上有一个同心结。

A pair of thieves were conspiring to rob us. 有两个贼预谋盗窃我们的东西。