第1个回答 推荐于2017-11-24
这三个词用于表达时间in 1. 表示一天的某个部分如：I work more efficiently in the morning 我早晨工作效率更高些I am going to have a meeting in the afternoon 下午我有个会议2. 用于较长的时间，如星期，月，季，处或世纪等They are going to attend the short-term training courses in the September 他们将于九月去参加短期培训班People usually sleep on the sidewalks in Wuhan in the summer夏季武汉人常睡在人行道上3. 还可以用来表示某事再过多久将要发生或某事要花多少时间I will see you again in a week's time 过一星期我还要和你见面I will give it back to you in two hours 我将在两个小时后把它还给你You must bring the book in two weeks 你过两星期必须把书还回来on1. 表示在一周中星期几，某月中几号，某个节日或节日的夜晚I will come back on Thursday我星期四回来 The ceremony was performed on April 15仪式是4月15日举行的My sister brought me a big cake on my birthday我姐姐在我生日时给我送来一个大蛋糕2. 如果未指明具体某一天的上午，下午或傍晚时，也要用 on 而不用 in I remember he arrived on a Monday morning我记得他是在一个星期一的早晨到的On a warm aftenoon in May ,I was seized with restlessness五月里一个温暖的下午，我感到坐卧不安On the night I have nothing particular to do ,I often go for a walk在无事可做的晚上，我常常出去散步It happened on Saturday evenin 此事发生在星期六的傍晚注： on 用于指某一天的傍晚，而in 则用于泛指点一般的傍晚。在last next this 之前 on 须省略I saw him last May去年五月我见到了他I will see you next Sunday下个星期天再见at 1. 表示时间的一个点：时刻We are going to meet at eight tomorrow morning我们打算在明天早晨八点碰头She will be home at exactly half past nine她将在九点半准时到家Some people are used to working at night 有些人习惯于夜间工作At the bigining of that month,I was sick那个月初我生病了2. 指周末或节日I will entertain you at the weekend这个周末我请你吃饭 She received a lot of gifts from her students at Christmas 圣诞节她收到了许多学生送的礼物3. 表示年岁I left home at the age of fifteen我十五岁就离开了家In China a person comes to age at eighteem在中国年满十八岁成年The poet died at thirty years of age 那个诗人三十岁就去世了本回答被网友采纳
第2个回答 2014-02-26
in+地点为 在某地(加大地点)如in cities/in town；in the sth为 在某物里面；in the +早中晚为 在早|中|晚；on+具体的某一天或某一天的早中晚（直接加），如：on Sunday\on Sunday afternoon;on+sth为 在某物上面。at +几点、at+某地（小地点）如：at school/at home; at the moment为此时，用时放在句末,和now差不多（now既可放句首，也可放句末。放句首时，后面加逗号）如：I'm doing my homework at the moment=I'm doing my homework now=Now,I'm doing my homework.这几个介词的用法还有很多很多，举不胜举，就不一一列举了。你以后会学到的。
第3个回答 2019-04-28
in+季节或月份或年
on+具体的一天
at+时间点（几点几分）
a+第一个音标是辅音的单词单数
an+第一个音标是元音的单词单数