1、介词是一种虚词。不能单独作句子成分，它只有跟它后面的宾语一起构成介词短语，才能在句子中起作用。
有：in, on, under, with, behind, about, near, before, after, for, to, up, down, from, in front of, out of, from…to…, at the back of…
2、表示时间的介词有：at, on, in。
（1）at表示“在某一个具体的时间点上”，或用在固定词组中。如：at ten o’clock, at 9:30 a.m., at night, at the weekend…
（2）on表示“在某日或某日的时间段”。如：on Friday, on the first of October, on Monday morning…
（3）in表示“在某一段时间（月份、季节）里”。如：in the afternoon, in September, in summer, in 2005…
3、in一词还有其他的固定搭配，如：in blue（穿着蓝色的衣服），in English（用英语表达），take part in（参加）。
练一练：
1、选用括号内恰当的介词填空。
1) What’s this _______ ( at, on, in ) English?
2) Christmas is _______ ( at, on, in ) the 25th of December.
3) The man_______ ( with, on, in ) black is Su Hai’s father.
4) He doesn’t do well _______ ( at, on, in ) PE.
5) Look at those birds _______ ( on, in ) the tree.
6) We are going to meet _______ ( at, on, in ) the bus stop _______ ( at, on, in ) half past ten.
7) Is there a cat _______ ( under, behind, in ) the door?
8) Helen’s writing paper is _______ ( in, in front of ) her computer.
9) We live _______ ( at, on, in ) a new house now.
10) Does it often rain _______ ( at, on, in ) spring there?
2、圈出下列句子中运用不恰当的介词，并将正确的答案写在横线上。
1) Jim is good in English and Maths.
2) The films were in the ground just now.
3) They are talking to their plans.
4) How many students have their birthdays on May?
5) Women’s Day is at the third of March.
6) I can jog to school on the morning.
7) Did you water trees at the farm?
8) Can you come and help me on my English?
9) I usually take photos in Sunday morning.
10) What did you do on the Spring Festival?
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