on,at,in这三个常用介词都可以表示时间和地点,但具体用法不同,多数学生对它们混淆不清.现在只要记住了口诀,就可避免at,on,in的种种误用.
1. on,in,at表示时间
on“在具体某一天
”① “当某时”,动名词, arrival,death前；early,late位句先②,用in一般“上”“下”“晚”；on用于天,in用于月busily、季、年③；限定三时in要变.④at是个时间点,“工作”“时刻”与“圣诞”⑤.at noon（night）,in the day,习惯用语记心间.
注：①on表示在具体某一天及具体某一天的上午、下午和晚上.
例 On mother’sDay, we should send flowers to our mother. 母亲节,我们应该送花给我们的母亲.
On my arrival home,I found he had gone already．当我到家时,我发现他已经走了.
② 当early,late用于句首修饰介词短语时,尽管表示具体某一天的上午、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． 国庆节一清早,我便起床去赶到动物园的第一班公共汽车.
My father begins work at 8：00 in the morning and stops work at 4：00 in the afternoon． 我父亲上午8点上班,下午4点下班.
③于将来时态表示“过一段时间后” 及表示“在……期间” 和“在某个季节,某年、某月” 都用in.
例 I hear he’ll be back in a month．我听说他将于一个月后回来.
In the course of the last lesson in French,little Franz was listening to the master very attentively．在那最后一堂法语课中,小弗朗兹非常用心地听着老师讲.
Xiao Ming was born in December of 2004. 小明生于2004年12月.
④当 morning,afternoon,evening有前位定语或后置定语限定时,就不用in而用on.
例 on a hot (summer) noon 在一个炎热（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 表示某时某刻及在work,Christmas前用at.
例 We get up at eight o’clock． 我们8点起床.
My father are busily at work all day． 我父亲整天忙于工作.
In western countries children get present from their parents at Christmas． 在西方国家,孩子们在圣诞节得到父亲给的礼物.
My Hometown
My hometown is beautiful place It stands near a wide river at the foot of low green hills. It has many tall buildings and wide streets. There are trees and flowers everywhere.
But it has not always been like that. In the old days, it was a sad dirty little town. Landlords and merchants lived in the few good houses. For the working people there were only dark, unhealthy rooms in old buildings and huts in narrow muddy streets. Nearly everyone was poor and many had no work.
Everything has changed since liberation. The people, led by the Party, have got rid of the mud and dirt. They have put up schools, theaters, shops and flats. They have an assembly hall and a hospital. Along the river they have built offices, hotels and parks. A lot of factories have sprung up. On the river, streamers and boats come and go busily, day and night. They carry the products of our industries to all parts of the country.
I love my hometown, and I love its people. They also have changed. Healthy and happy, they are going all out to build socialism.