which與as在定語從句中的不同用法
下面是小編整理的一些關於which與as在定語從句中的用法，希望幫助大家區分這兩個單詞。提高英語水平。
一、which與as用法相同點
1. as和which都能引導定語從句，並都可以在定語從句中做主語或賓語，代表前面整個句子。
例 1 He married her, as / which was natural. 他跟她結婚了，這是很自然的事。
例 2 He is honest, as we can see. 他很誠實， 這一點我們看得出來。(表示人們從日常主觀常識, 經驗對某一事情的看法、評價,用as爲妥。)
2. 當非限定性定語從句置於句末時，as和which都可用來引導這個定語從句。
例 3 The number of senior high school students is increasing, as is mentioned above. (as引導非限定性定語從句，意思是“正如”。此時也可以換用which引導，但意思有別，意思是：“這一點上面提到了”。)
二、which與as用法不同點
(一)語義上的區別
as作爲關係代詞仍多少保留 “理由”“比較” “方式” “等同”等意義，而which沒有這些意義。因此，由as引導的定語從句通常在意義上不可與主句相悖，而且一般是肯定的，對主句意義起相輔作用，表示 “正如”等意義;而which引導從句則不受此限制。
例 4 Mother treats me just like a baby，which I can’t bear. 媽媽對我就像小孩，我真受不了。
例 5 She has married again，which was unexpected. 她又結婚了，這是大家沒有預料到的。
上面兩句中的which都不宜用as。
但當否定的定語從句作正面理解，對主句起相輔作用而不是與其相悖時，仍可用as。
例 6 He turned his eyes on Philip’s face，as he had not done for ten years.他轉過身來看着菲利普的臉，他十年來沒有這樣看過他的臉了。
例 7 He really can’t lend you the money，as you might not realize. 他的確不能把那些錢借給你，這一點你可能意識不到。
(二)用法上的區別
1. which與as引導非限制性定語從句的區別：
(1)which只能放在主句後面，而as引導的從句位置相對比較靈活，可以放在前，也可以放在後，甚至還可以分割主句。另外，as 常常有“正如、正像”的含義。
例 8 As he realized, I was very useful to him.(在前)
例 9 Air, as we know, is a gas. (在中)
例 10 He was a foreigner, as I know from his accent. (在後)
例 11 He came late again, which made his boss angry.(在後)
例 12 As is known to all, China is a developing country. 衆所周知，中國是發展中國家。
(2)在which引導的定語從句中，謂語動詞若是am, is, are，則這些系動詞不能省略，而as後面若是這種情況，則可以省略。
例 13 He is a teacher, as (is) clear from his manner. (is可以省略)
例 14 He said he had never seen her before, which was not true. (was 不可省略)
(3)當which引導的從句在意義上近乎並列關係時，可以用and this, and that代替，意思是“這件事”。
例 15 He changed his mind, which(and this, and that) made me very angry. 他改變了主意，這使我很生氣。
而as主要起與上下文連接的作用，表達說話人的看法、觀點，並指出主句內容的出處或根據等。
例 16 Einstein, as we know, is a famous scientist.愛因斯坦，衆所周知，是一位偉大的科學家。
例 17 As is announced in today’s newspaper, we must improve our style of work. 今天的報紙上說，我們必須改進工作作風。
(4)做主語時，which既可以作系動詞be的主語，也可以作實義動詞的主語，而這時as 只可以做系動詞be的主語。
例 18 He married her, which was natural. (可用as代替which)他和她結婚，這是很自然的事。
例 19 He won a /the Nobel Prize in chemistry, which made him illustrious. (不可用as代替which)他獲得了諾貝爾化學獎，這使他名揚天下。
(5)當定語從句位於主句之後，純粹表示主句所述的內容，不帶有“如……那樣”的意思時，往往用which, 而不用as。
例 20 They were invited to the state banquet, which(as) was a great honor to them. 他們被邀請參加國宴，這對他們來說是莫大的榮幸。
例 21 We had to sleep in our wet clothes, which was most uncomfortable. 我們不得不穿着溼衣服睡覺，這簡直太不舒服了。
(6)當定語從句有“如同……那樣”的含義時，用as比用which更常見，而這些從句幾乎成爲固定說法。
例 22 Things will turn out contrary to one’s wishes, as is often the case. 事與願違，這是常有的事。
例 23 As was natural, this inordinate hope was followed by an excessive depression.這種過分希望之後，接着是極度的沮喪，是很自然的事。
例 24 The material is elastic, as is show in the figure. 這種材料有彈性，如圖所示。
例 25 As we know. 衆所周知。
例 26 As has been said above/ before. 正如前文所述 。
(7)當定語從句的關係代詞指的是先行詞本身時，只能用which。
例 27 These apple trees, which I planted tree years ago, have not borne any fruit.這些蘋果樹是我三年前種下的，沒結出任何果實。
例 28 The Thames, which is now clean enough to swim in, was polluted for over a hundred years.泰晤士河，現在已經很乾淨，可以在裏面游泳，它曾被污染了一百多年。
(8)帶介詞的典型的定語從句，必須用which，不能用as。
例 29 There is a great deal of oxygen around us, without which we could not live. 我們周圍有許多氧氣，沒有它我們就無法生存。
例 30 The shed in our garden, in which we often played, has lasted for a long time. 我們經常玩耍的花園裏的那個棚子，已經有很長時間了。
(9)as常與從句中的know，see， hear，expect等動詞連用，也常用於as often happens，as is often the case(常有的事)等句子中;而which一般不用於以上情況。
例 31 As is well known，Shanghai is a big city.
(10)當後置的非限制性定語從句是否定結構時，只能用which引導。
例 32 The result of the experiment was very good, which we hadn’t expected.
2. 引導限制性定語從句時which與as的區別：
(1)先行詞如果是表示物的名詞或代詞，在從句中又做介詞的賓語時，只能用which。
例 33 This is the pan in which I boiled the milk. 這就是我煮牛奶的鍋。
(2)前面有as時,引導定語從句的關係代詞用as, 不用which。
例 34 There are as many dictionaries as are needed.所需要的字典都有了。
(3)前面有such時，引導的定語從句的關係代詞用as, 不用which。
例 35 Such women as know Tom thought he was charming. 認識湯姆的女人都認爲他很迷人。
例 36 I have never heard such stories as he tells. 他講的那些故事我從沒聽過。
(4)前面有the same時，引導定語從句的關係代詞用as而不用which。
例 37 We are facing the same problems as we did years ago.我們正面臨着和多年以前同樣的困難。
例 38 This is the same wallet as I lost. 這隻錢包與我丟失的那隻相同。
(5)單個詞引導限制性定語從句時，一般不用as而用which和that。由於關係詞在從句中作賓語，which和that都可以省略。
例 39 The project which/that a British businessman has invested in is under construction at present.
(6)“介詞+關係代詞”引導定語從句時，只能用which。
例 40 Recently I bought an ancient Chinese vase, the price of which was very reasonable.
注：此時的which不能用as來代替。另外還應注意：引導定語從句時，which不能單獨作定語，此時不管先行詞是人還是物，都只能用whose引導，但指物時，可以用of which替換。
