25 用逗號(hào)隔開(kāi)——非限制性定語(yǔ)從句　Track 025

作用：用來(lái)提供附加而非必要信息，只是對(duì)先行詞作進(jìn)一步的解釋、補(bǔ)充或說(shuō)明。若去掉此定語(yǔ)從句，整個(gè)主句意義仍然很明確，不會(huì)引起誤解和歧義。
例句
a. Beijing, which is the capital of China, has developed into an international city.
b. My mother, who is 50 this year, lives with me now.
c. Einstein, who was a great Jewish scientist, came up with the theory of relativity.
d. Hawaii, which consists of eight principal islands, is a favorite vacation spot.
以上各句中的定語(yǔ)從句都是在對(duì)其前面的先行詞進(jìn)行補(bǔ)充說(shuō)明，向讀者提供附加信息，均不能變?yōu)橄拗菩远ㄕZ(yǔ)從句。比如，若說(shuō)My mother who is 50 this year lives with me now.則讓人理解為“我有好幾位母親，目前和我住在一起的是今年50歲的那位。”
總的原則：如果定語(yǔ)從句修飾一個(gè)專(zhuān)有名詞，我們一般要用逗號(hào)隔開(kāi)，也就是說(shuō)要用非限制性定語(yǔ)從句。這是因?yàn)閷?zhuān)有名詞本身意思已經(jīng)很完整，不需要限制，定語(yǔ)從句只是對(duì)它進(jìn)行補(bǔ)充。