介词 on at in 表时间at 时间最短，一般表示点时间，具体的某个时刻1.at six oclock2.at 8:30习惯用语：at night at noon at this time of yearOn 在具体某一天 及 具体某一天的上午 下午 和晚上1.On mothers Day ,we should send flowers to our mother.2.On Monday/Friday/Saturday3.On Tuesday afternoon On Sunday morning (evening)4.On July 1,1999 On March 7On + 星期(1-7)On + 年，月，日 / 年，日 / 月，日In 时间范围大（一天以上）1.in spring/ summer/ autumn/ winter2.in 1999/ 2012 in May ,20123.in the morning /afternoon/ evening 4.in September/ May/ June/ July5.in a year in a week1 in +四季2 in +月份3 in +年 / 年，月 / 月 At 1天 On=1天介词 on at in 表方位at 把地点，地方，位置当做一个点1.He is at home.2.He is waiting for you at the bus stop.3.Whos standing there at the door.4.Im in France,at paris.On 把地点，地方，位置当作一个平面1 There was a No Smoking sign on the wall.2I live on the 7th floor at 21 Oxford street in London.3You are standing on my foot.4 There are no prices on this menu.in把地点，地方，位置当作一个范围或一个封闭的空间1.I live in London2.I live in England, at London. 3.I live in a big city,my sister lives at a small town.