同位語從句的位置與定語從句的比較：
1、同位語從句與定語從句一樣,都是用在名詞后面.所不的就是：定語從句是修飾限制它前面的名詞,因此,它是屬于形容詞從句.而同位語從句屬于名詞性從句,它是用來 .說明它前面的名詞內(nèi)容的,或者說是解釋前面名詞的內(nèi)容.
2、同位語從句只用that作為開頭（I have no idea除外）,屬于連詞,在從句中不起成分作用,但不可省略.而定語從句是以關(guān)系代詞開頭,關(guān)系代詞在從句中起句子成分作用（作主語、賓語或表語）,作賓語時可以省略.
3、只有在內(nèi)容方面可以進一步闡明的名詞（一般為抽象名詞）才能帶同位語從句,而幾乎任何名詞都可以帶定語從句.
比較：
(1)The suggestion (that) she has given at the meeting is good.
(2)The suggestion that she should stay in the room is good.
(1)句中that she has given at the meeting這個從句說明了是她提出的建議,不是別人的建議,也就是限定了the suggestion的范圍,但并沒有說明建議的內(nèi)容.從結(jié)構(gòu)上分析,that是give的賓語,所以這個從句是定語從句.
(2)句的that she should stay in the room這個從句說明了建議的內(nèi)容,同時,that只起連詞作用,在從句中既不是主語,也不是賓語,但不能省略,所以它是同位語從句.
二、同位語從句前常用的名詞：
同位語從句說明的名詞常見的有：ability, advice, answer,belief, doubt, discovery, fact, fear, hope, idea, information, message,news, order, possibility, problem, proposal, question, story, suggestion, theory, thought, word(消息)等.而不可說明的名詞是不會接同位語從句的.比如：man, water, sun等具體的人或事物.例如：
There is no doubt that the prices of cars will go down.
The belief that the company will make a great is shared by everyone.
三、where, when, why, how, who, what等在引導同位語從句時,一般只用于I have no idea結(jié)構(gòu)中,其實,這種類型的同位語從句應(yīng)該列入賓語從句的范疇,因為I have no idea意思就是I don't know...
如：I have no idea where I should go.
I have no idea how I can get to the railway station.
四、有時候主句的謂語比較短,同位語從句比較長,這個從句就不一定緊接在它所說明的名詞后面.如：
Word(消息) came that our Chinese women team had beaten Japanese.