五、介词：常用介词：in, on, at, behind等
1.at表示时间概念的某一个点。(在某时刻、时间、阶段等)。
at 1：00(dawn，midnight，noon)在一点钟(黎明、午夜、中午)
2.on
1)表示具体日期。
注：(1)关于"在周末"的几种表示法：
at(on)the weekend 在周末---特指
at(on)weekends 在周末---泛指
over the weekend 在整个周末
during the weekend 在周末期间
(2)在圣诞节，应说at Christmas?而不说on Christmas?
2)在(刚……)的时候。
On reaching the city he called up his parents.
一到城里他就给父母打了一个电话。
3.in
1)表示"时段"、"时期"，在多数情况下可以和during互换，前者强调对比，后者强调持续。 in(during)1988(December，the 20th century)在一九八八年(十二月、二十世纪)
六、动词：动词的四种时态
(1)一般现在时：
一般现在时的构成
1. be动词：主语+be(am, is, are)+其它。如： I am a boy. 我是一个男孩。
2. 行为动词：主语+行为动词(+其它)。 如： We study English. 我们学习英语。
当主语为第三人称单数(he, she, it)时，要在动词后加"-s"或"-es"。如：Mary likes Chinese.玛丽喜欢汉语。
动词+s的变化规则
1.一般情况下，直接加-s，如：cook-cooks, milk-milks
2.以s. x. sh. ch. o结尾，加-es，如：guess-guesses, wash-washes, watch-watches, go-goes
3.以“辅音字母+y”结尾，变y为i, 再加-es，如：study-studies
(2)一般过去时:
动词过去式详解 动词的过去式的构成规则有：
A、规则动词
①一般直接在动词的后面加ed：如 worked , learned , cleaned , visited
②以e结尾的动词直接加d：如 lived , danced , used
③以辅音字母加y结尾的动词要改y为i再加ed(此类动词较少)如 study – studied carry – carried worry – worried (注意play、stay不是辅音字母加y,所以不属于此类)
④ 双写最后一个字母(此类动词较少)如 stopped
B、不规则动词(此类词并无规则，须熟记)小学阶段要记住以下动词的原形和过去式：
sing – sang , eat – ate ，see – saw , have – had , do – did , go – went , take – took , buy – bought , get – got , read – read ,fly – flew , am/is – was ,are – were , say – said , leave – left , swim – swam , tell –told , draw – drew , come – came , lose – lost , find – found , drink – drank , hurt – hurt , feel – felt
(3)一般将来时：
基本结构：
①be going to + do;
②will+ do. be going to = will
I am going to go swimming tomorrow(明天). = I will go swimming tomorrow.
(4)现在进行时: am,is,are+动词现在分词
动词现在分词详解 动词的ing形式的构成规则：
①一般的直接在后面加上ing , 如doing , going , working , singing , eating
②以e 结尾的动词，要先去e再加ing ，如having , writing
③双写最后一个字母的(此类动词极少)有：running , swimming , sitting , getting