子句，“从句”的旧称(台、港仍沿用)。在某些语言(如英语)它是复合句的一个成分,自有其主语和谓语,尤指其公用同名词、形容词或副词者。

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COBOL语言中一个语句的一部分,用以说明一基本项的结构,分别对独立的或成组的工作区暂存区给予初始值,或者重新定义由其他子句原来定义过的数据。

我们讨论子句时会用到的字

基本上,我们将子句分为独立子句 (independent clauses)和从属子句 (dependent clauses)；这意谓有些子句可以单独存在,有些则不行.独立子句又称为主要子句 (main clauses 或 principal clauses),而从属子句又称为附属子句 (subordinate clauses)--意谓附属子句必须依附主要子句才能存在.附属子句是由附属连接词 (subordinating conjunction,又称从属字 dependent word：如 because, and, but, yet, so 等 ) 来产生.

子句也被分为限定子句 (restrictive clauses) 与非限定子句 (nonrestrictive clauses).有两个字有时也被用来分别表达跟 restrictive 和 nonrestrictive 相同的意思,那就是 「必要」(essential) 和「非必要」( nonessential).一个非限定子句对句子的意思并非必要,它可从句子中移除而不会改变句子的基本意思. 非限定子句通常用一个逗点与句子的其他部分分开,或者前后各用一个逗点分开 (如果它是放在句子中间的话).

Professor Villa, who used to be a secretary for the President, can type 132 words a minute.

关系子句 (relative clauses) 是由一个关系代名词 (relative pronoun：that, which, whichever, who, whoever, whom, whomever, whose, of which等) 所引导的附属子句.关系子句可以是限定或非限定子句.读者可以参考「逗点的使用规则」,裨在决定关系子句是限定子句或非限定子句,以及是否使用逗点来将它们与句子的其他部分分开时,可以获得更多的协助.在关系子句中,关系代名词是动词的主词 (记住：所有子句都有主词与动词的关系)且与该子句前面的人事物有关.

Tom said that the plantar wart, which had been bothering him for years, had to be removed.

精减子句 (Elliptical clauses)：见下面的说明.

独立子句 (Independent Clauses)

独立子句可做为单独的句子存在,只是当它们与其他子句分离而单独存在时,它们通常被称为句子,而不叫子句.我们必须学会辨认子句并知道一个子句何时可以做为独立子句,这有助於我们写出正确的句子.例如,在下面的句子中,

Bob didn't mean to do it, but he did it anyway.

子句系利用三种不同的方式来结合：对等、附属及使用分号 (；).对等 (coordination) 是指以一个对等连接词 (and, but, or, nor, for, yet, so)来结合独立子句.利用这种方式连接的子句在长度和意思 (import) 上通常具有良好的对等.

Ramonita thought about joining the church choir, but she never talked to her friends about it.

附属 (subordination) 是指利用一个附属连接词 (有时称为附属字) 或一个关系代名词将其中一个子句变成附属子句.当某一子句系以附属或从属字做开头时,他就不再是独立子句；它被称为附属或从属子句,因为它的意思系依附独立子句而定.我们还可利用其他方法来结合子句,如将独立子句变成各种修饰用的片语.

Although Ramonita often thought about joining the choir, she never talked about to her friends about it.

Ramonita never talked to her friends about joining the choir, because she was afraid they would make fun of her.

Yasmin is Ramonita's sister. Yasmin told Ramonita to join the choir no matter what her friends said.

利用关系子句来结合：

Yasmin, [who is] Ramonita's sister, told Ramonita to join the choir...

分号 (semicolon) 可以在连接副词 (conjunctive adverb,亦称语气转折字 transitional expression：however, moreover, nevertheless 等) 的协助下 (但也可以不必藉助於连接副词) 连接两个独立子句.但分号应尽量少用,而且只有当两个独立子句在长度和意思上关系非常密切且具有良好的对等关系时才使用.

Ramonita has such a beautiful voice; many couples have asked her to sing at their wedding.

Ramonita's voice has a clear, angelic quality; furthermore, she clearly enjoys using it.

从属子句 (Dependent Clauses)

从属子句不能单独存在.它们必须与独立子句结合,成为一个可以单独存在的句子的一部份.与独立子句不同的是,附属子句系被用来在句子中担任不同的功能.它们可以当名词用或当修饰语用.根据它们在句子中的功能,我们可以分类出三种基本的从属子句.请记住：一个从属子句一定包含一个主词和一个动词,但它不能单独存在.

1.名词子句当主词 What they did with the treasure remains a mystery.

Whatever you want for dessert is fine with me.

That you should feel this way about her came as a great surprise to us.

2.名词子句当受词 Juan finally revealed what he had done with the money.

Her husband spent whatever she had saved over the years.

I don't know what I should do next.

3.名词子句当介系词的受词 In fact, he wrote a book about what he had done over the years.

We are interested in what he does for a living.

4.名词子句当述语主格 (predicate nominative) -- 即主词补语 The trouble was that they had never been there before.

The biggest disappointment of last season was that the

women's team didn't make it to the final four.

5.形容词子句 My brother, who now teaches math in a small college, never liked math in high school.

The dealership that sold more cars ended up actually losing money.

The Federated Bank, which was founded nearly two

centuries ago, folded during the state's economic crisis.

6.副词子句 The team had fallen behind by ten points before they were able to figure out the opponent's defense.

Since he started working nights, he doesn't see much of his kids.

While Josie sat inside watching television, Gladys shoveled the driveway.

精减子句 (Elliptical Clauses)

精减子句是文法不完整的子句,因为它们省略了通常用来引导这种子句的关系代名词 (从属字) 或一项比较中第二部分的述语 (predicate).精减子句中省略的部分可以从上下文中猜测出来,而大多数读者也不知道什麼东西不见了.事实上,精减子句被视为一种有用且正确的子句,即使在正式的文章中亦然,因为它们通常是优雅和有力的表达方式.在下面的句子中,被省略的字用括号括起来.

Coach Rodman knew [that] this team would be the best [that] she had coached in recent years.

Though [they were] sometimes nervous on the court, her recruits proved to be hard workers.

Sometimes the veterans knew the recruits could play better than they [could play].

Which Vs. That

Which 这个字可被用来引导限定子句与非限定子句,不过许多写作者仅用它来引导非限定子句；That 这个字只能被用来引导限定子句.看看下面这两个句子之间到底有什麼不同：

The students that study most usually do the best.