1.表示比较：as，like，above，over，with
She was something like her sister.她有几分像她的妹妹。
Chinese is much more difficult in contrast with English.和英语相比，汉语难得多。
2.表示条件：with，without
Without your advice，he would have failed.没有你的忠告他可能已经失败了。
With your help，I might succeed.如果有你的帮助，我可能会成功。
3.表示目的：as，for
I only said it as a joke.我只是把它当作笑话讲的。
It’s time for class.到上课的时间了。
4.表示让步：for，with
For all his effort，he didn’t succeed.虽然他做了一番努力，仍不能成功。
With all his money，he is unhappy.尽管他有钱，但他并不快乐。