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；early,late位句先②,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.④at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 send 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． 在西方國家,孩子們?cè)谑フQ節(jié)得到父親給的禮物.