on,at,in這三個(gè)常用介詞都可以表示時(shí)間和地點(diǎn),但具體用法不同,多數(shù)學(xué)生對(duì)它們混淆不清.現(xiàn)在只要記住了口訣,就可避免at,on,in的種種誤用.
1.on,in,at表示時(shí)間
on“在具體某一天”①
“當(dāng)某時(shí)”,動(dòng)名詞,arrival,death前；
用in一般“上”“下”“晚”；
on用于天,in用于月、季、年③；
限定三時(shí)in要變.④
at是個(gè)時(shí)間點(diǎn),
“工作”“時(shí)刻”與“圣誕”⑤.
at noon（night）,in the day,
習(xí)慣用語記心間.
注：①on表示在具體某一天及具體某一天的上午、下午和晚上.
例 On Mother's Day,we should sned flowers to our mother.母親節(jié),我們應(yīng)該送花給我們的母親.
On my arrival home,I found he had gone already．當(dāng)我到家時(shí),我發(fā)現(xiàn)他已經(jīng)走了.
② 當(dāng)early,late用于句首修飾介詞短語時(shí),盡管表示具體某一天的上午、下午、晚上,都要用in,泛指一般的上、下午,晚上也用in .
例 Early in the morning of National Day,I got up to catch the first bus to the zoo． 國(guó)慶節(jié)一清早,我便起床去趕到動(dòng)物園的第一班公共汽車.
My father begins work at 8：00 in the morning and stops work at 4：00 in the afternoon． 我父親上午8點(diǎn)上班,下午4點(diǎn)下班.
③于將來時(shí)態(tài)表示“過一段時(shí)間后” 及表示“在……期間” 和“在某個(gè)季節(jié),某年、某月” 都用in.
例 I hear he’ll be back in a month．我聽說他將于一個(gè)月后回來.
In the course of the last lesson in French,little Franz was listening to the master very attentively．在那最后一堂法語課中,小弗朗茲非常用心地聽著老師講.
Xiao Ming was born in December of 2004.小明生于2004年12月.
④當(dāng) morning,afternoon,evening有前位定語或后置定語限定時(shí),就不用in而用on.
例 on a hot (summer) noon 在一個(gè)炎熱（夏天）的中午
on Monday Morning 在星期一上午
on the morning of March 8th在3月8日上午
⑤ 表示某時(shí)某刻及在work,Christmas前用at.
例 We get up at eight o’clock． 我們8點(diǎn)起床.
My father are busily at work all day． 我父親整天忙于工作.
In western countries children get present from their parents at Christmas． 在西方國(guó)家,孩子們?cè)谑フQ節(jié)得到父親給的禮物.
2.on,in,at表示地點(diǎn)
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(diǎn),“入口、車站、電影院”③；
home出現(xiàn)定語、冠,須用in把a(bǔ)t換④；
“夜間、車輛”若有限,及“在途中”on在前⑤.
注：①在表示地點(diǎn)時(shí),指“在……之上（與表面接觸）” “靠近、接壤”及“在左右邊”都用on.
例 There is an English-Chinese dictionary and two grammar books on the big desk．那張大寫字臺(tái)上有一本英漢詞典和兩本語法書.
Korea lies on the northeast of China． 朝鮮位于中國(guó)東北方.
Tom was sitting on my left when we saw the film yesterday． 我們昨天看電影時(shí),湯姆坐在我左邊.
②表示“在……里面”（即物體內(nèi)部）,“在……中間”（即middle前）都用in.
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(dòng)一下,打開了門.
Soon they were in the middle of the river． 很快他們就游到了河中間.
③ at表示一個(gè)較小的地點(diǎn),如在“入口”（entrance）“車站”（bus stop,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 entrance to a valley． 她往前走時(shí),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(shí),須用in.
例 In Princeton he lived quietly,working at the institute and enjoying himself 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(jiǎn)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 He was in on that night． 他那天夜里在家.
My son often goes to school on his bike．我兒子常騎自行車去上學(xué).
On the way home my father told me of an incident that took place 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(shí)發(fā)生的一件事