首先定義『什麼是子句？』答：『A clause is a group of words containing a subject and a verb』。翻譯成中文：『子句』就是包含主詞和動詞的一堆字。等一下，你說，包含主詞和動詞？這不就是一個句子（sentence）嗎？是的是的，一般的 sentence 也是子句的一種，稱為『主要子句』（main clause）。
子句本身不能獨立存在，非得依附在主要子句上才能生存。舉個簡單的例子：『When I got home, my cat came to welcome me.』其中『when I got home』就是一個時間子句 -- 有主詞、有動詞，但顯然不是一個完整的句子 -- 我們可以說完『when I got home』就畫上句點嗎？當然不可以！『當我回家』...然後呢？然後呢然後呢？說話說一半，聽起來就像是重心不穩要跌倒！要怎麼讓它站穩呢？就是加上後半句的『my cat came to welcome me』。注意『my cat came to welcome me』是這個句子裡的主要子句，所以獨立存在也沒問題（亦即，『My cat came to welcome me.』本身就是一個完整的句子）。
什麼是形容詞子句（adjective clause）呢？就是用來形容名詞的子句。例如：
(1) The boy kissed Mary yesterday.
(2) The boy is wearing a blue scarf.
我們可以將 (1) 當作主要子句，把這兩個句子合併為『The boy who is wearing a blue scarf kissed Mary yesterday.』其中『who is wearing a blue scarf』就是一個用來描述『the boy』的形容詞子句 -- 它本身有主詞有動詞，但不是一個完整的句子。如果要將 (2) 當作主要子句當然也可以，那麼合併後的句子就是：『The boy who kissed Mary yesterday is wearing a blue scarf.』這兩個句子裡隱含的資訊完全一樣，但是語氣不同。第一句強調他親吻了瑪莉，第二句則強調他今天戴了藍圍巾。通常主要子句就是造句者想強調的主題。
為什麼要學形容詞子句呢？因為如果完全不用形容詞子句，我們常會寫出許多短小的句子，讀起來不順暢；若適當地運用形容詞子句，可以把一些短小的句子塞進主要子句當中，使整句話長度適中且內容豐富，念起來更流暢。
形容詞子句可用下列特殊字開頭：who（用於人，主格）、whom（用於人，受格）、which（用於東西，主受格同形）、whose（所有格，可用於人或東西）、that（用於人或東西皆可，主受格同形，唯其前不可接介係詞）
例句：
(1) I like the boy. The boy is sitting in the front row.
= I like the boy who is sitting in the front row.
(2) I don't know the girl. Peter is talking to the girl.
= I don't know the girl whom Peter is talking to.
= I don't know the girl who Peter is talking to. （受格 whom 可用主格 who 代替）（反之不然）
= I don't know the girl to whom Peter is talking. （受格前若有介係詞可搬到受格前）
= I don't know the girl Peter is talking to. （受格也可以直接省略）
(3) I'm interested in the topic. You're talking about the topic.
= I'm interested in the topic which you're talking about.
(4) I pick up the pencil. The pencil was dropped on the floor.
= I picked up the pencil which was dropped on the floor.
(5) I met a boy. The boy's hairstyle was really weird.
= I met a boy whose hairstyle was really weird.
另外 when/where 是比較特殊的，它們都是以一個單字取代『介詞 + which』兩個字，但是 when 表示時間、where 表示地點。例如：
(6) I enjoyed the hotel. We stayed in the hotel for honeymoon.
= I enjoyed the hotel in which we stayed for honeymoon.
= I enjoyed the hotel where we stayed for honeymoon.
(7) I can't remember the day. We met on that day.
= I can't remember the day on which we met.
= I can't remember the day when we met.
上面這些例句的形容詞子句都有「描述」的功能，如果拿掉形容詞子句，原來的句子仍然是完整的句子，但是意思卻會變得模糊。例如 (1) I like the boy. 如果只說到這裡，我們會搞不清楚到底是哪個男孩？加上後半的 who is sitting in the front row 就清楚明白了：坐在前排的那個男孩。但有時候容詞子句也可以做為額外的補充說明，即使丟掉這個形容詞子句，意思也完全不改變。此時就會在形容詞子句的前後加上逗號，表示語氣停頓，逗號後面的說明與逗號前的名詞是同一個東西（同位語）。看一個簡單的例子：
(1) Students who are lazy should be failed.
(2) Students, who are lazy, should be failed.
這兩個句子的意思有差別嗎？當然！
(1)：懶惰的學生應該被當掉。（勤奮的學生可以過關）
(2)：學生是懶惰的，應該被當掉。（所有的學生都懶惰，所有的學生都應該被當掉）
在例句 (2) 中，用逗號包圍起來的 who are lazy 是額外的資訊，可以整包丟掉，丟掉之後變成『Students should be failed.』 -- 所有的學生都應該被當掉。
所以逗號非常重要啊，可能會徹底改變句子的意義！不可不慎！當你要判斷『到底要不要加逗點』的時候，可以試著把形容詞子句丟掉，看看意義有沒有改變？如果沒有，就可以加逗點。
我記得高中老師教到這個部份的時候，曾經說過『如果描述的名詞有很多個，就不加逗點；如果只有一個就要加逗點』。背誦的例句是：
(1) My brother who lives in London got married last month. （我有很多哥哥，住倫敦的那個結婚了）
(2) My brother, who lives in London, got married last month. （我只有一個哥哥，他住在倫敦）
不過我還是覺得『把整個形容詞子句拿掉、看看意義是否改變？若完全相同就是要加逗號』這個方法比較容易。例如上句 (1)，如果你本來有很多哥哥，但只有住倫敦的那個結婚，寫成『My brother got married last month.』就變得模糊不清 -- 到底是哪個哥哥呢？住紐約那個嗎？住倫敦那個嗎？還是住金瓜石那個？
再一個例句：
(1) Mary has two children whose names are John and Tom.
(2) Mary has two children, whose names are John and Tom.
例句 (1) 表示瑪莉有好幾個小孩，其中兩個叫約翰和湯姆（沒有說其他小孩叫什麼名字）。
例句 (2) 表示瑪莉只有兩個小孩，名字分別是約翰和湯姆。
我們可以把例句 (2) 的形容詞子句整個拿掉 -- 它只是告訴我們兩個小孩的名字，不改變瑪莉有兩個小孩的事實；但是例句 (1) 的形容詞子句是必要的，否則瑪莉的其它小孩就消失了。
另外一個記憶『需不需要逗點』的方法是：凡是專有名詞，都需要逗點（因為專有名詞一定是指特定的某個人事物）。例如：
Mr. Jones, who is my sister's husband, lives in Paris, which is the capital of France.
這個句子一共有三個子句（一個主要子句、兩個形容詞子句），但是重點（主要子句）是『瓊斯先生住在巴黎』，所以若把兩個被逗點包圍的形容詞子句全部丟掉也沒關係。（中間的『我妹夫』是為了怕你不知道瓊斯先生是誰；最後的補充則是怕你不知道巴黎是法國首都。）
which 也可以用來指『前面說過的整句話』，這個時候就一定要加逗點以示區隔。例如：
Jack said he had been kidnaped by aliens, which is really bullshit!
最後，形容詞子句（adjective clause）可以被縮短成形容詞片語（adjective phrase）。縮短之後，句子變得更精鍊，但是意義完全不變。修改形容詞子句為片語的方法很簡單：如果原本的形容詞子句裡有 be 動詞（is/am/are/was/were），就把形容詞裡的主詞（who/which/that）和 be 動詞都刪掉即可；若原本的子句裡沒有 be 動詞，則掉動詞改成動名詞（V-ing）。（我記得高中老師的講法是：若子句裡的動作是主動，則用 V-ing，若被動則用 V-pp。兩種講法稍有不同，但最後得到的結果相同。）
【註1】如果形容詞子句的主詞與主要子句的主詞不同，則不能縮短喔！！
【註2】如果縮短後的形容詞片語只剩一個形容詞，則通常會搬去要形容的名詞前面（前位修飾）
例句：
(1) I like the boy who is sitting in the front row.
= I like the boy sitting in the front row.
(2) I picked up the pencil which was dropped on the floor.
= I picked up the pencil dropped on the floor.
(3) The policeman caught the thief who stole my bike.
= The policeman caught the thief stealing my bike.
(4) I don't know the girl whom Peter is talking to.
= 不能縮短！因為 the girl 與形容詞子句的主詞（Peter）不是同一人！
(5) I know a girl who is beautiful.
= I know a beautiful girl. （把 who is 刪掉後只剩 beautiful，所以要搬到它要形容的 girl 之前。）
雖然說形容詞片語往往比形容詞子句更加精鍊，但在改寫的過程中，有時會損失原本子句的『時態』，這時候就要自行斟酌是否要改寫。例如上述例句 (1)，如果原句是 I like the boy who was sitting in the front row. 那麼改成片語之後得到的結果會和例句 (1) 的結果一樣：I like the boy sitting in the front row. 但因為損失了 be 動詞，所以我們可能會誤會說話的人是指現在坐前排的那個男生而非昨天坐前排的那個。但若這句話有前後文對照，也許我們就知道作者在說現在還是昨天，即使損失了 was 也無損原句意義。所以要自行斟酌是否用子句或片語。
當子句的時態是完成式時，通常就不修改為片語，因為那樣損失了原來的意義。
好啦！以上就是所有的形容詞子句的課程。以下是習題，不太容易喔！有興趣的人可以做做看：運用形容詞子句或片語，將下列題目中的句子合併為一個句子。畫底線的句子必須是主要子句。注意標點符號。
1. Disney World covers a large area of land.
It is an amusement park.
It is located in Orlando, Florida.
The land includes lakes, golf courses, campsites, hotels, and a wildlife preserve.
=> Disney World, an amusement park located in Orlando, Florida, covers a large area of land including lakes, golf courses, campsites, hotels, and a wildlife reserve.
2. Jamaica is one of the world's leading producer of bauxite.
It is the third largest island in the Caribbean Sea.
Bauxite is an ore.
Aluminum is made from this ore.
=> Jamaica, the third largest island in the Caribbean Sea, is one of the world's leading producer of bauxite, an ore from which aluminum is made.
3. Robert Ballard made headlines in 1985.
He is an oceanographer.
In 1985 he discovered the remains of Titanic.
Titanic was the "unsinkable" passenger ship.
It has rested on the floor of the Atlantic Ocean since 1912.
It struck an iceberg in 1912.
=> Robert Ballard, an oceanographer, made headlines in 1985 when he discovered the remains of Titanic, the "unsinkable" passenger ship which has rested on the floor of the Atlantic Ocean since 1912 when it struck an iceberg.
4. William Shakespeare's father was a glove maker and a town official.
William Shakespeare's father is John Shakespeare.
He owned a shop in Stratford-upon-Avon.
Stratford-upon-Avon is a town.
It is about 75 miles northwest of London.
=> (1) William Shakespeare's father, John Shakespeare, was a glove maker and a town official who owned a shop in Stratford-upon-Avon, a town about 75 miles northwest of London.
=> (2) William Shakespeare's father, John Shakespeare, who owned a shop in Stratford-upon-Avon, a town about 75 miles northwest of London, was a glove maker and a town official.
(1) 和 (2) 在文法上都是完全正確，但是 (1) 比 (2) 好得多。因為 (2) 把主要子句的頭尾拉得太遠了，會讓人感到困惑，摸不著頭腦。所以 (1) 的寫法比較理想。
5. The Republic of Yemen is an ancient land.
It is located at the southwestern tip of the Arabian Peninsula.
This land has been host to many prosperous civilizations.
These civilizations include the Kingdom of Sheba and various Islamic empires.
=> The Republic of Yemen, located at the southwestern tip of the Arabian Peninsula, is an ancient land which has been host to many prosperous civilizations including the Kingdom of Sheba and various Islamic empires.
留言列表
