下面說說這三個介詞在表示地點時用法的區(qū)別,口訣如下：
on,in,at表地點,on“在之上”接觸面,
“靠近、接壤、左右邊”①； in“在里面”和“中間”②；
at表示小地點,“入口、車站、影劇院”③；
home出現(xiàn)定語、冠,須用in把at換④；
“夜間、車輛”若有限,及“在途中”on在前⑤.
說明：
①在表示地點時,指“在……之上（與表面接觸）”.例：
There is an English－English dictionary and two grammar books onthe big desk．那張大寫字臺上有一本英語詞典和兩本語法書.
“靠近、接壤”及“在左右邊”都用on.例：
Korea lies on the northeast of China．朝鮮位于中國東北方.
Tom was sitting on my left when we saw the film yesterday．我們昨天看電影時,湯姆坐在我左邊.
②表示“在……里面”（即物體內(nèi)部）.例：
Jim turned the key in the lock and opened the door．吉姆把鑰匙插在鎖孔里,轉(zhuǎn)動一下,打開了門.
“在……中間”（即middle前）都用in.例：
Soon they were in the middle of the river．很快他們就游到了河中間.
③at表示一個較小的地點,如在“入口”（entrance）“車站”（busstop,railway station）和“影劇院”（cinema,theater）等名詞前.例：
As she walked along,she noticed an old pine tree ahead at the en－trance to a valley．她往前走時,注意到前邊峽谷口有棵老松樹.
④home前一般用at,但若有物主代詞和冠詞等定語修飾時,須用in.例：
In Princeton he lived quietly,working at the institute and enjoyinghimself by playing his violin in his simple home．他在普林斯頓過著安靜的生活,在研究所工作,在他那簡樸的家里拉琴消遣.
⑤“夜間”（night）、“車輛”（bus,bike,train ect．）等名詞若有限定詞及“在……途中”,介詞則用on.例：
1）He was in on that night．他那天夜里在家.
2）My son often goes to school on his bike．我兒子常騎自行車去上學(xué).
3)On the way home my father told me of an incident that tookplace on his first day at school in Mr Crossett’s class．在回家途中,父親給我講了他第一天上克羅塞特先生課時發(fā)生的一件事.1、Lucy can write a letter___Japanese though she has learned it only a few months.
A.from B.to C.in D.with
2、They will have an English test___two days.
A.for B.at C.in D.after
3、Wu Dong was born___the evening of April 2,1975.
A.at B.in C.on D.to
答案：ccc