used to + do："过去常常"表示过去习惯性的动作或状态，但如今已不存在。
　　Mother used not to be so forgetful.　　
　　Scarf used to take a walk.　 (过去常常散步)
be used to + doing： 对……已感到习惯，或"习惯于"，to是介词，后需加名词或动名词。
　　He is used to a vegetarian diet.　　
　　Scarf is used to taking a walk.(现在习惯于散步)
典型例题　　　
---- Your phone number again? I ___ quite catch it.

1）在确定的过去时间里所发生的动作或存在的状态。
　 时间状语有：yesterday, last week, an hour ago, the other day, in 1982等。
　 Where did you go just now?
2）表示在过去一段时间内，经常性或习惯性的动作。
　 When I was a child, I often played football in the street.
　 Whenever the Browns went during their visit, they were given a warm welcome.　　　　　
3）句型：
　 It is time for sb. to

现在进行时的基本用法：
　a. 表示现在( 指说话人说话时) 正在发生的事情。
　　 We are waiting for you.
　b. 习惯进行：表示长期的或重复性的动作，说话时动作未必正在进行。
　　 Mr. Green is writing another novel.　
　　　(说话时并未在写，只处于写作的状态。)
　　 She is learning piano under Mr. Smith.
　c. 表示渐变的动词有：get, grow, become, turn, run, go, begin等。
　　 The leaves are turning red.
　　 It's getting warmer and war

1) 构成will / be going to do sth.
　2) 概念　
　　a. 状态完成：表示某事继续到将来某一时为止一直有的状态。
　　b. 动作完成：表示将来某一时或另一个将来的动作之前，已经完成的动作或一获得的经验。
　　　They will have been married for 20 years by then.
　　　You will have reached Shanghai by this time tomorrow.

1)　两个动作如按顺序发生，又不强调先后，或用then，and，but 等连词时，多用一般过去时。
　　 When she saw the mouse，she screamed.
　　 My aunt gave me a hat and I lost it.
2 ) 两个动作相继发生，可用一般过去时；如第一个动作需要若干时间完成，用过去完成时。
　　 When I heard the news, I was very excited.
3)　叙述历史事实，可不用过去完成时，而只用一般过去时。
　　 Our teacher told us that Columbus discovered America in 1492.

1） 概念：表示过去的过去
----|-------|-----|---->其构成是had +过去分词构成。
那时以前　 那时　现在　　　　　　
2） 用法
　a.　在told, said, knew, heard, thought等动词后的宾语从句。
　　 She said (that) she had never been to Paris.
　b. 状语从句
　　 在过去不同时间发生的两个动作中，发生在先，用过去完成时；发生在后，用一般过去时。
　　 When the police arrived, the thieves had run away.
　c. 表示意向的动词，如hope, wish, expe

1) 用于完成时的区别
　　延续动词表示经验、经历； 瞬间动词表示行为的结 果，不能与表示段的时间状语连用。
　　 He has completed the work.　　他已完成了那项工作。 (表结果)
　　 I've known him since then.　　 我从那时起就认识他了。(表经历)
2)　用于till / until从句的差异
　　 延续动词用于肯定句，表示"做……直到……" 瞬间动词用于否定句，表示"到……，才……"
　　 He didn't come back until ten o'clock.
　　　　他到10 点才回来。
　　 He slept until ten o'clock.　　　　　

1) since +过去一个时间点　(如具体的年、月、日期、钟点、1980, last month, half past six)。
　 I have been here since 1989.
2) since +一段时间+ ago
　 I have been here since five months ago.
3) since +从句　
　 Great changes have taken place since you left.
　 Considerable time has elapsed since we have been here.
4) It is +一段时间+ sinc

Since 用来说明动作起始时间，for用来说明动作延续时间长度。
　　I have lived here for more than twenty years.
　　I have lived here since I was born..
　　My aunt has worked in a clinic since 1949.　
　　Some new oilfields have been opened up since 1976.
　　I have known Xiao Li since she was a little girl.　
　　My brother has been in the Youth League for two years.

1）It is the first / second time…. that…结构中的从句部分，用现在完成时。
　 It is the first time that I have visited the city.
　 It was the third time that the boy had been late.
2）This is the… that…结构

1）过去时表示过去某时发生的动作或单纯叙述过去的事情，强调动作；现在完成时为过去发生的，强调过去的事情对现在的影响，强调的是影响。
2）过去时常与具体的时间状语连用，而现在完成时通常与模糊的时间状语连用，或无时间状语。
一般过去时的时间状语:
yesterday, last week，…ago, in1980, in October, just now, 具体的时间状语
共同的时间状语:　
this morning, tonight,this April, now, once，before, already, recently，lately　
现在完成时的时间状语
for, since, so far, ev

现在完成时用来表示之前已发生或完成的动作或状　态，其结果的确和现在有联系。动作或状态发生在过去　但它的影响现在还存在；也可表示持续到现在的动作或　状态。其构成： have (has) +过去分词。

意为："意图"、"打算"、"安排"、常用于人。常用词为 come, go, start, arrive, leave, stay等。
　 I'm leaving tomorrow.
　 Are you staying here till next week?

1）下列动词：come, go, arrive, leave, start, begin, return的一般现在时表将来。这主要用来表示在时间上已确定或安排好的事情。
　　　The train leaves at six tomorrow morning.
　　　When does the bus star? It stars in ten minutes.
2）倒装句，表示动作正在进行，如：
　　　 Here comes the bus. = The bus is coming.
　　　 There goes the bell. = The bell is ringing.
3）在时间或条件句中。
　　　 When Bill co

be to 表示客观安排或受人指示而做某事。
　　 be going to 表示主观的打算或计划。
　I am to play football tomorrow afternoon.　　 (客观安排)
　I'm going to play football tomorrow afternoon. (主观安排)