在这里，我们谈一个比较普遍的问题，即有关现在完成时与作“自从”解的 since 连用的问题。关于这个问题，有些情况在一般语法书中都有讲解，所以我们对这些情况只拟简单地举例说明一下。有些情况则在一般语法书中或未涉及，或语焉不详，所以我们将对这些情况多费一点笔墨。
总的来说，现在完成时与 since 连用时，其用法有两大类：一是表持续的动作或状态，这时 since 有“自从……起一直不断地”的含义；一是表非持续的动作或状态，这时 since 的意思则是“在过去某一时间与现在之间”，没有“一直不断地”的含义。
表持续动作或状态的这种现在完成时，概括地说，又有两种不同的用法。一是所用动词必须是持续动词（或叫做无限动词），如：
(1)She has taught us since I came to this school.
(2)I have been ill since last Sunday.
一是所用动词可以是非持续动词（或叫做有限动词），多用于否定结构，如：
(3)He has never touched beer since last month.
(4)Nothing has happened since then.
关于现在完成时与 since连用时表持续的用法，就简要地归纳如上。现在就让我们谈谈现在完成时与 since连用时表非持续的问题。关于现在完成时与 since连用时表非持续的动作或状态，又可以分做两小类来讲：
第一小类是多用非持续动词表重复的动作和状态，这是我们常可见到的，如下面句子中主句所用的现在完成时：
(5)I have met him often since I have lived here.
(6)I have gone camping twice since I have owned a bicycle.
(7)Since we came to this school we have had three headmasters.
(8)Since the end of last year, over 5 billion trees have been planted all over the country.
下面句子中的现在完成时也有重复的性质：
(9)I must attend to work that has accumulated since I have been away.
(10)I have learnt a lot since I have known him.
(11)I have had much practice in English composition since I have kept a diary.
第二小类是多用非持续动词表过程和结果，这也是并不罕见的，如：
(12)The corporation has shown remarkable results since starting six years ago.
(13)Since last year it （the city's women's federation）has raised an anti-gambling army of 140,000 women organized into 3,293 teams.
(14)Since here I've heard that some people in Shanghai would like it to be Hong Kong.
(15)Since last I wrote to you I have seen the ruins of Rome.
(16)I have considered , ever since I have been capable of serious reflection.
(17)Since my writing the above, something has occurred of a most unexpected and serious nature.
(18)The town has changed since 1949.
(19)What have you done since yesterday?
(20)What's happened since yesterday?
(21)Since when have you become active in politics?
(22)Fully a century has passed since mason's hand has touched it.
(23)Has he had any illness since I have been gone?
(24)The Cubans have given the champions （China's national women's volleyball team）some real trouble since Los Angeles.
(25)Since the beginning of this year, there has been a sharp increase in the number of ship passengers, and tickets have not been easily available.
(26)The first edition of the Persian translation of China's “Daodejin” （《道德经》）by Lao Zi has been sold out since its printing here （in Tehran）seven months ago in 4,000 copies.
读者读到这里可能要问：为什么为这一类的现在完成时不厌其烦地举了这么多例证呢？ 我们这样做主要有两个原因：一是中国学生对现在完成时（与 since 连用时）的这种用法可能还不甚熟悉；第二个原因更为重要，即不是任何非持续动词皆可这样地用现在完成时。换言之，有些非持续动词的现在完成时就不能与 since 连用。如动作短暂的 open, close, leave, miss, find, lose, get 等动词的现在完成时一般皆不可与 since连用。例如应该说：
(27)I have left the door open since ten minutes ago. （自然也可说 I have opened the door 或 I opened the door ten minutes ago, 但不可说 I have opened the door since ten minutes ago）
但请注意 raise, hear, see, occur, change, happen, become, pass, give, sell 等动词的现在完成时却可与 since 连用，分别如上述例（13）、（14）、（15）、（17）、（18）、（20）、（21）、（22）、（24）、（26）。 这是为什么呢？难道这些动词的动作不也是短暂的吗？是的，孤立地看，它们都是动作短暂的动词，但当它们放在不同的句子中时，它们就有时强调一单纯动作之结束，有时则强调其动作虽已结束，但其影响仍旧存在，而从动作到影响则有一个过程。且以 change 为例。如说：
(28)I changed my address last year.
句中的 changed 只表一个单纯动作的结束，仅此而已，与现在毫无关系。但如说：
(29)I have changed my address since last year.
句中的 have changed 则与现在有关了。它不但表其动作已结束，而且意味着句中的主语I现今的地址仍是去年所变换的那个地址。这就是我们所谓的现在完成时的影响或结果。
由此可以看出，同是表短暂动作的动词，有的只强调这一短暂的动作，而其现在完成时不可与 since 连用来表过程和结果；有的则有二重性，它们不但可以强调一个短暂的动作，而且其现在完成时可与 since连用表示一个过程和结果。而这正是一般语法书所未涉及的。
但问题到此并未完全了结。再请看下面两个句子：
(30)I've got to know him since last year.
(31)And since when have you begun to hold up our hearts as trustworthy guides for us?
一般说来，动词 get 和动词 begin 显然只应强调一个短暂的动作，没有上述的二重性，但为什么它们的现在完成时在此也可以与 since连用表示过程和结果呢？语言是复杂的。 begin 和 get 的确与上面所说的 open 一样，其现在完成时一般是不能与 since一起表过程和结果的，但如果其后的不定式是持续动词，情况就不同了。你看，例（30）的 have got 之后的不定式 to know 即是持续动词；例（31）的 have begun 之后的不定式 to hold up 也是持续动词，而这两个不定式的重要性显然大于其前的 have got 与 have begun。所以这两个句子中表示过程和结果以及持续的正是它们，而 have got 与 have begun，正如某些语法家所说的那样，所起的作用可以说是相当于助动词了。
最后一个问题似乎更加微妙了。你看，我们可以说：
(32)I have graduated from college since we met.也可以说：
(33)Since then I have graduated from college.
但却不可说“I have graduated from college since 2000.”这又是为什么呢？原来有的表短暂动作的非持续动词与具体时间或日期连用时，其动作性特别强，只能表动作的结束，不能表过程和结果，而graduate 就是其中之一，所以只能说：
(34)I graduated from college in 2000.
但当这种动词的现在完成时与不表具体时间或日期的 since 连用时，则可表过程和结果，如上述例（32）和（33）。
所以，当现在完成时与 since 连用表过程与结果时，所用的非持续动词又可分为两小类：一小类是可以与后接什么都可以的 since 连用；一小类则是只可以与后接表非具体时间的词语的 since 连用。
上面谈了这么多种类的非持续动词，但到底那些种类有哪些动词，我们则须对具体问题做具体分析，机械划一的规则是没有的。
