此句point后为何用where？这是什么句子：定语从句or同位语从句？求详细解释！~

关系副词where引导的定语从句修饰point。

point在此的意思是：an exact moment, time, or stage in something's development （时间）点；时刻；（发展的）阶段；程度；地步 如：

We can use this document as a starting point for our discussions.

我们可以从这份文件开始讨论。

to the point of...到...阶段（程度，地步）

The beams had weakened to the point of being dangerous.

那些横梁已经老化到危险地地步。

你给的句子中的point和这句话中point用法是相同的，因为to the point在此意思是 “到达某种程度，阶段，地步”，point相当于指一个（地）点，所以关系词用where（=everyone else is sick of it at this point)。

原句意为：

如果汤姆找到一首喜欢的歌，他可能就会一边一边地听，直到其他所有人都听恶心了！

同位语从句一般用that引导，它和that引导的形容词从句主要区别是：

that在同位语从句中是连词，只起连接作用，没有具体词义。而that在形容词从句中是关系代词，在从句中充当一定得成分，并有相关词义。例如：

The news that was spreading proved to be incorrect. （that指news，在从句中作主语。）

The news that he was resigning his position proved to be incorrect. （同位语从句that只起引入从句的作用。）

不定式主动表被动：

去分词与现在分词被动式的区别

(1)过去分词在构成完成时态,不定式完成式以及被动语态时,通常不能用现在分词一般被动式代替.(现在进行时的被动语态除外)

eg：The door was closed an hour ago．

这门在一小时前就关闭了.

They have finished their homework.

他们已经做完了家庭作业

(2)过去分词作前置定语时,不能用现在分词一般被动式代替.

eg：That was an inspired suggestion．

那是一条由某人提出的建议.

同样现在分词一般被动式作为定语表示动作时,也不能用过去分词来代替.

eg：The house being built is a big project.

正在施工的那幢楼是一项大的工程.

(3)过去分词作条件、时间等状语时,不可用现在分词一般被动式代替.

eg：Given more time,I can do it better．(表条件)'

多给点时间,我会做得更好些.

Given more attention,the trees could have grown better.(表示条件)

如果多关心一些,这些树会长得更好.

Heated ,the metal expands．(表示时间)

加热后,这种金属会膨胀.

Asked why he did it,he said it was his duty ．(表示时间)

问及为何要做此事时,他说这是他的职责.

(4)过去分词作表语时,不能用现在分词一般被动式代替.

eg：The top of the mountain is covered with snow .山顶满是雪.

(5)过去分词在构成have,get,want等动词后的复合宾语时,不能用现在分词一般被动式.

eg：Why don’t you have the radio fixed?

你为什么不把收音机拿去修一修?

尤其是一些感官动词,如：see,hear,find等后构成复合宾语时,过去分词和现在分词一般被动式意思完全不同.

eg:I heard this song being sung by my students in the next room.

我听到隔壁房间的学生正在吟唱这首歌.

(注：现在分词一般被动式表示正在进行的动作)

I have never heard this song sung in English．

我从来没有听到过用英语唱这首歌.

(注：过去分词表示己完成的动作)

(6)在下面一些比较固定的分词独立结构中,通常多用过去分词.

eg:all told总计

all things considered考虑了一切因素之后

this accomplished完成这项工程之后

this explantion given这样解释之后

all said and done毕竟

二．过去分词和现在分词完成被动式的区别：

及物动词的过去分词没有完成式,但它有“完成”的含义,所以它可以代替现在分词完成被动式.

eg:The bridge had been weakened by successive storms and was no longer safe .

Weakened by successive storms,the bridge was no longer safe.

Having been weakened by successive storms,the bridge was no longer safe.

这座桥接二连三地遭到暴风雨的袭击后,己经不安全了.

但若强调分词表示的行为发生在后一个动词表示的行为之前时,可用现在分词完成被动式.

eg:Having been warned about the bandits,he left his valuables at home.

当警告有强盗出没时,他就把贵重物品留在家里.

通常过去分词可作定语使用,而现在分词完成被动式却不能用作定语.

eg:The computer centre,opened last year,is very popular among the students in this school.

去年开办的计算机中心很受学生的欢迎.

(过去分词既能表示被动又有完成的含义)

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