一、同位語(yǔ)從句的定義和特點(diǎn)

在主從復(fù)合句中作同位語(yǔ)的從句稱(chēng)為同位語(yǔ)從句。

同位語(yǔ)從句一般用that, whether，what, which, who, when, where, why, how 等詞引導(dǎo)，常放在fact, news, idea, truth, hope, problem, information, wish,promise, answer, evidence, report, explanation, suggestion, conclusion等抽象名詞后面，說(shuō)明該名詞的具體內(nèi)容。換言之，同位語(yǔ)從句和所修飾的名詞在內(nèi)容上為同一關(guān)系，對(duì)其內(nèi)容作進(jìn)一步說(shuō)明。

例：The news that they had won the game soon spread over the whole school.
他們比賽獲勝的消息很快傳遍了整個(gè)學(xué)校。
析：they had won the game說(shuō)明The news的全部?jī)?nèi)容，因此該句為同位語(yǔ)從句。

二、正確運(yùn)用同位語(yǔ)從句的引導(dǎo)詞，準(zhǔn)確把握同位語(yǔ)從句

引導(dǎo)同位語(yǔ)從句的連接詞

?

 功能 例詞
從屬 連詞 ?? 只起連接作用，不充當(dāng)從句中的任何成分。 that, whether
連接 代詞 既起連接作用，又在從句中擔(dān)任成分（主語(yǔ)、賓語(yǔ)、表語(yǔ)或定語(yǔ)）。 who,? what? ，whose, which
連接 副詞 既起連接作用，又在從句中擔(dān)任成分（狀語(yǔ)）。 when,? where, why, how ???
復(fù)合代詞 & 復(fù)合副詞 既起連接作用，又在從句中擔(dān)任成分（主語(yǔ)、賓語(yǔ)、表語(yǔ)或定語(yǔ)、狀語(yǔ)）。 ?whoever, whatever, whichever, whenever, wherever, however

1.如同位語(yǔ)從句意義完整，應(yīng)用that引導(dǎo)同位語(yǔ)從句。（即that 不充當(dāng)任何成分，只起連接作用，不可省略）

例：The general gave the order that the soldiers should cross the river at once.
將軍下達(dá)了戰(zhàn)士們立即過(guò)河的命令。
析：the soldiers should cross the river at once是the order的全部?jī)?nèi)容，且意義完整，因此應(yīng)用that引導(dǎo)同位語(yǔ)從句。

2.如同位語(yǔ)從句意義不完整，需增加"是否"的含義，應(yīng)用whether引導(dǎo)同位語(yǔ)從句。（if不能引導(dǎo)同位語(yǔ)從句）

例：We'll discuss the problem whether the sports meeting will be held on time.
我們將討論運(yùn)動(dòng)會(huì)是否會(huì)如期舉行的問(wèn)題。
析：the sports meeting will be held on time意義不完整，應(yīng)加"是否"的含義才能表達(dá)the problem的全部?jī)?nèi)容，因此應(yīng)用whether引導(dǎo)同位語(yǔ)從句。

3.如同位語(yǔ)從句意義不完整，需增加"什么時(shí)候"、"什么地點(diǎn)"、"什么方式"等含義，應(yīng)用when, where, how等詞引導(dǎo)同位語(yǔ)從句。

例1：I have no idea when he will be back.
析：he will be back意義不完整，應(yīng)加"什么時(shí)候"的含義才能表達(dá)idea的全部?jī)?nèi)容，因此應(yīng)用when引導(dǎo)同位語(yǔ)從句。

例2：I have no impression how he went home, perhaps by bike.
析：he went home意義不完整，應(yīng)加"如何"的含義才能表達(dá)impression的全部?jī)?nèi)容，因此應(yīng)用how引導(dǎo)同位語(yǔ)從句。

4.當(dāng)主句的謂語(yǔ)較短，而同位語(yǔ)從句較長(zhǎng)時(shí)，同位語(yǔ)從句常后置。
如：The thought came to him that maybe the enemy had fled the city.

三、把握同位語(yǔ)從句和定語(yǔ)從句的區(qū)別，明確同位語(yǔ)從句和相似從句的界限

同位語(yǔ)從句和定語(yǔ)從句相似，都放在某一名詞或代詞后面，但同位語(yǔ)從句不同于定語(yǔ)從句。同位語(yǔ)從句對(duì)名詞加以補(bǔ)充說(shuō)明，是名詞全部?jī)?nèi)容的體現(xiàn)，且名詞和同位語(yǔ)從句的引導(dǎo)詞均不在從句中作成分；定語(yǔ)從句說(shuō)明先行詞的性質(zhì)與特征，與先行詞是修飾與被修飾的關(guān)系，且名詞和定語(yǔ)從句的引導(dǎo)詞均在從句中作成分。

區(qū)分時(shí)可以在先行詞與從句之間加一個(gè)系動(dòng)詞be,使之構(gòu)成一個(gè)新句子，如果句子通順且符合邏輯，則為同位語(yǔ)從句，反之，則為定語(yǔ)從句。

如：The report that he was going to resign was false.
因?yàn)閠he report was that he was going to resign 句意通順，所以，that he was going to resign 是同位語(yǔ)從句。

四、典型例題

1. Some researchers believe that there is no doubt____ a cure for AIDS will be found.
A. which B. that C. what D. whether

2. A warm thought suddenly came to me ____ I might use the pocket money to buy some flowers for my mother's birthday．
A. if B. when C. that D. which

3. Nobody believed his reason for being absent from the class ________ he had to meet his uncle at the airport.
A. why? B. that　C. where D. because

4. Along with the letter was his promise _______ he would visit me this coming Christmas.
A. which B. that C. what D. whether

5. Danby left a word with my secretary ____________ he would call again in the afternoon.
A. who B. that C. as D. which