先行詞為不定代詞、先行詞是形容詞級或被形容詞級修飾、先行詞是序數(shù)詞或其被序數(shù)詞修飾、先行詞被the very， the only等詞修飾、先行詞包含了人和事物兩方面的含義、先行詞被same修飾，且指“同一物品”、關(guān)系代詞在定語從句中作表語、主句是以who，which開頭的特殊疑問句或先行詞是who。

當(dāng)先行詞為all, much, none, something, nothing, everything, the one, few, little, many, anything等不定代詞時。例如：

We should do all that is useful to the people. 我們應(yīng)該做一切有益于人民的事情。

當(dāng)先行詞被only, any, few, little, no, all, many, much等不定代詞修飾時。例如：

I have finished reading all the books that I borrowed from the library. 我己經(jīng)看完了所有從圖書館借來的書。

當(dāng)先行詞被序數(shù)詞、形容詞最高級以及the only, the very, the next, the last等修飾時。例如：

This is the first book that I bought in the shop . 這是我在這家書店買的第一本書。

當(dāng)先行詞是形容詞最高級時。例如：

This is the best that can be done now.這是現(xiàn)在能做的最好的辦法。

先行詞既指人又指物時。例如：

We talked of things and persons that we remembered. 我們談起了我們記住的人和事兒。

關(guān)系代詞在限制性定語從句中作表語，并帶有比較的含義時。例如：

Our school is no longer the school that it was ten years ago .我們學(xué)校已經(jīng)不再是十年前的樣子。

句子的前一部分已經(jīng)出現(xiàn)了which,為避免重復(fù)，句子的后面部分通常不再用 which而用that來引導(dǎo)限制性定語從句.例如：

Which is the book that you bought yesterday? 哪一本書是你昨天買的？

當(dāng)主句是以who , which 引起的特殊疑問句時，關(guān)系代詞通常只用that. 例如：

Who is the man that you spoke to just now? 剛才和你說話的那個人是誰？