表示特指，例如：

1、On the face of it， it seems like a great deal.表面上看来好像很多。

2、You've got something on the end of your nose.你的鼻尖上有个东西。

3、I'm doing some research on the subject.我正就这一课题进行研究。

4、Work has begun on the construction of the new airport.新机场的修建已经开工。