across表示横过,即从物体表面通过，与on有关;
through穿过,即从物体内部穿过，与in有关。
She swam across the river.
He walked through the forest.
4.表示“在……之间”的介词：between, among
between指在两个人或两个事物之间;
among指在三个或三个以上的人或事物之间。
There is a football match between Class One and Class Two on the playground.
The teacher is standing among the students.
5.表示其他意义的介词
1)on ,about 关于
on 表示这本书，这篇文章或演说是严肃的，或学术性的，可供专门研究这一问题的人阅读;
about表示内容较为普通，不那么正式。
There will be a lecture on economics this afternoon.
He is writing a book on cooking.
He told me a lot about his life in the summer vocation.
2)by, with, in 表示方法、手段、工具
by 以……方法、手段或泛指某种交通工具;
with 表示用 …工具、手段，一般接具体的工具和手段;
in 表示用…方式，用…语言(语调、笔墨、颜色)等;
He makes a living by selling newspapers.
He broke the window with a stone.
The foreigner spoke to us in English.
3)except, besides 除了
except 除……之外，不包括在内;
besides 除……之外，包括在内。
Except Mr. Wang, we went to see the film.(王先生没去)
Besides Mr. Wang, we also went to see the film.(王先生也去了)
