1.短暂性动词，延续性动词和现在完成时短暂性动词是指动作一旦发生就立即结束。它不能和一段时间连用。
这类动词有：go, come, arrive, leave, begin, start, join, marry 等；短暂性动词的肯定式不能与表示一段时间的for或since或how long等状语连用。
例如：His father got ill. I have received his letter.
但是，不可以说：
His father got ill for a week.I have received his letter for three days.
在否定句中，短暂性动词可以和表示一段时间的状语连用。
例如：We haven’t heard from Jane for a long time.I suppose something must have happened to her.
2.延续性动词是指动作发生后还可以延续一段时间或者相当长的一段时间。
如：live, work, study, learn, sleep等，延续性动词可以和表示一段的时间状语连用。
表示一段时间的状语:
for+一段时间
since+n./从句（时间点）
since+时间段+ago
疑问词how long
in the past+时间段
all these+时间段
from…to（时间点）
till/until+n./句子等等。
例如：How long _______ your brother joined the army?
A. has B. had C. is it since D. was there that
通过审题，答案B和D很容易被排除，但是稍不注意便会选中答案A；殊不知how long为一段时间的状语，不能与非延续性动词短语has joined连用，所以这题的正确答案是C。
另外，动词的延续性与非延续性还体现在这两种句型中：
延续性动词的肯定式+till/ until
短暂性动词的否定式+till/ until
请看例句：We waited until he came.I didn’t go to bed until my father came back home last night.
如果短暂性动词与表示一段时间的时间状语连用，必须将短暂性动词改为延续性动词。现归纳总结一下由非延续性动词到延续性动词的转换： arrive→be here begin(start)→be on die →be dead come back→be back
leave →be away (from)
fall ill(sick, asleep)→be ill(sick, asleep) get up→be up go out →be out finish →be over
put on →wear 或be on open →be open join →be in或 be a member of… close →be closed go to school→be a student borrow →keep buy/get →have catch(a cold)→ have(a cold) get to know →know begin to study→study come to work→workmove to → live in finish/end → be overcome to → be in sit down → be seatedmarry → be married dress → be dressed等
如：He has been a soldier for three years. 他参军三年了。 His father has been dead for two years. 他父亲去世二年了。 The film has been on for t
en minutes. 电影已开始十分钟了 We have studied English for three years. 我们（开始）学英语已三年了。
How long can I keep this book? 这本书我可以借多长时间？
除了用上面的转化形式之外，还可以用其他的表达形式：A. It is/ has been+时间+since……（动词用过去式），B. 主语+谓语（过去时）+时间+ago。 例如：It’s five days since I received his letter.His father died three years ago.看一个句子可以用以下几种说法：他离开上海已经3天了。He left Shanghai three days ago.He has been away from Shanghai for three days.He has been away from Shanghai since three days ago.It is/ has been three days since he left Shanghai.Three days has passed since he left Shanghai.几点注意事项:（1）have been(to)与have gone( to)的区别：have been(to)表示“去过某地（现在已经回来了）”，可用于各人称；have gone(to)表示“去某地了（说话时某人不在当地）”，可能在去的路上，可能已在某地，也可能在回来的路上，总之，人不在这里。常用第三人称作主语。，前者可与once ,never, several times等连用，后者则不能。如：They have been to Beijing twice. 他们去过北京两次。 He has gone to Beijing . 他去北京了。注意比较下面几组句子的意义：He has gone to Amercia. （他到美国去了。 他不在这里）He has been to Amercia. （他去过美国。 现已回来）He has been in Shanghai. （他在上海呆过。 现在不在上海）He has been in shanghai for years. （他在上海多年。 现在还在上海）He has taught English. （他教过英语 现在不教了）He has taught English for years. （他教英语多年了。 现在还在教）（2）如单纯表示一段时间，或强调一段时间，虽有since一词，也不必用完成时。如：It is two years since his father died.=His father has been dead for two years. 他父亲去世已有三年了。（3）终止性动词现在完成时的否定式，已变成一种可以延续的状态，因此可以和表示一段时间的状语连用。 如：I haven't left here since 1997. 自从1997年以来，我一直没有离开过这儿。
leave --- be away, borrow --- keep, buy --- have, begin/start --- be on, die --- be dead, finish --- be over, join --- be in+组织机构, be a member of+组织机构, open sth --- keep sth open, fall ill --- be ill, get up---be up, catch a cold --- have a cold, come here --- be here, go there --- be there, become --- be, come back --- be back, fall asleep --- be asleep, get to/ arrive/reach --- be (in), leave --- be away from, get to know --- know, go (get) out →be out， put on→ wear；catch a cold →have a cold等。 例:The old man died 4 years ago. ----The old man has been dead for 4 years. ---- It is 4 years since
the old man died. ----Four years has passed since the old man died. He joined the Party 2 years ago. -----He has been in the Party for 2 years. I bought the book 5 days ago. ---- I have had the book for 5 days.