非限定性定語(yǔ)從句：非限定性定語(yǔ)從句的作用是對(duì)所修飾的成分作進(jìn)一步說明,通常和主句間用逗號(hào)隔開,將從句拿掉后其他部分仍可成立
1.which引導(dǎo)的非限定性定語(yǔ)從句來說明前面整個(gè)句子的情況或主句的某一部分 ,that不能用于引導(dǎo)非限制性定語(yǔ)從句
例如:
She asked for his help which he gladly gave.她要求他幫忙,他愉快地幫助了她.
It was a century during which the country suffered continuously from wars.一個(gè)世紀(jì)過去了,在這期間這個(gè)國(guó)家不斷遭受戰(zhàn)亂之苦.
Attitudes towards daydreaming are changing in much the same way that(in which) attitudes towards night dreaming have changed.人們對(duì)白日做夢(mèng)的態(tài)度正在改變,這與人們對(duì)夜間做夢(mèng)的看法的變化有非常相似之處.
I like the music for the very reason that(for which) he dislike it.我出于某種原因喜歡這種音樂,而他恰恰與我相反.
We arrived the day that(on which) they left.剛好我們到的那天他們走了.
3.有時(shí)as也可用作關(guān)系代詞
4.在非限定性定語(yǔ)從句中,用who,whom代表人,用which代表事物.
5.當(dāng)先行詞是專有名詞或物主代詞和指示代詞所修飾時(shí),其后的定語(yǔ)從句通常是非限制性的.
例如：
Charles Smith,who was my former teacher,retired last year.查理·史密斯去年退休了,他曾經(jīng)是我的老師.
My house,which I bought last year,has got a lovely garden.我去年買的的那幢房子帶著個(gè)漂亮的花園.
This novel,which I have read three times,is very touching.這本小說很動(dòng)人,我已經(jīng)讀了三遍.
6.非限制性定語(yǔ)從句還能將整個(gè)主句作為先行詞,對(duì)其進(jìn)行修飾,這時(shí)從句謂語(yǔ)動(dòng)詞要用第三人稱單數(shù),
例如：
He seems not to have grasped what I meant,which greatly upsets me.他似乎沒抓住我的意思,這使我心煩.
Liquid water changes to vapor,which is called evaporation.液態(tài)水變?yōu)檎羝?這就叫做蒸發(fā).