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, fromto, 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 oclock, 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) Whats this _______ ( at, on, in ) English?
2) Christmas is _______ ( at, on, in ) the 25th of December.
3) The man_______ ( with, on, in ) black is Su Hais father.
4) He doesnt 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.
学识谷
