7、in the corner, on the corner, at the corner：in the corner 表示在角落里，in指角的内面；on the corner表示"在角上"，on指的不是内面，也不是外面，而含内外兼有之意；at the corner指"在拐角处"，at指的是拐角外附近的外面。如：The lamp stands in the corner of the room./ I met with him at the street corner./ He sat on the corner of the table.

6、表示"穿过……"的through和across：through表示从内部通过，与in 有关；across则表示从一端至另一端在表面上的通过，与on有关。如： Water flows through the pipe./ The old man walked across the street.

5、表示"在……上"的on和in：on只表示在某物的表面上，而用in表示占去某物一部分。 如：There is a book on the piece of paper./ There is an interesting article in the newspaper./ He dug a hole in the wall.

4、表示地理位置的in, on, to：in表示在某范围内，on指与什么毗邻，to指在某环境范围之外。如：Changchun is in the northeast of China./ Mongolia is on the north of China./ Japan is to the east of China.

3、表示时间的in和after：两者都表示"在（某个时间）之后，区别在于in表示"在（一段时间）之后"，而after则表示"在（某一具体时间点之后）"，in短语和将来时态连用，after短语和过去时态或将来时态连用。如：We'll be back in three days./ After seven the rain began to fall./ What shall we do after graduation?

注意：after有时也可以表示在一段时间之后（常用在过去时里）。如：After two months he returned.

2、表示时间的since和from：since表示从过去到现在的一段时间的过程，常与现在完成时连用。from表示从时间的某一点开始，不涉及与现在的关系。一般多与现在时、过去时、将来时连用。如：I hope to do morning exercises from today./ We have not seen each other since 1995.

1、表示时间的at, in, on：at表示片刻的时间，如：at 8 o'clock ，常用词组有：at noon, at night, at midnight, at the end of, at that time, at the beginning of, at the age of, at Christmas, at New Year等。in表示一段的时间，如：in the morning, in the afternoon, in the evening, in October, in 1998, in summer, in the past, in the future等。on总是跟日子有关，on Monday, on Christmas morning, on the following, on May Day, on a warm morning等。

4、作宾语补足语：I found him in the office.

（二）主要介词区别

3、作表语：My dictionary is in the bag.

2、作状语：We have breakfast at seven.（表时间）；They were late for meeting because of the heavy rain.（表原因）；They started the machine by pressing the button.（表方法）