所谓名词性从句，是指主语、表语、宾语和同位语扩展而成的句子，在复合句中形成从句，即主语从句、表语从句、宾语从句和同位语从句。
一、主语从句
1.以what，whatever，whoever，how等代词引导的主语从句，汉译时，一般可按原文顺序翻译。
How the advanced worker managed to raise production is of interest to us all.这位先进工人究竟是怎样提高生产的，我们大家对此很感兴趣。
Whatever form is used by the majority of educated speakers or writers is correct；or as Sweet puts it.“Whatever is in general use in a language is, for that reason, grammatically, correct.”大多数受过教育的人说话或写作时使用的英语就是正确的英语，或如斯威特所说：“凡是语言中广泛使用的说法（仅仅这一理由）都可以认为在语法上是正确的。”
2.以it作假主语所引起的真主语从句，可采取三种译法：a）译成宾语从句，b）译成并列分句，c）谓语分译，分述如下：
a）译成宾语从句有许多以it作形式主语而谓语是被动语态的句子，即“it+被动谓语+that”结构，其主语从句常常译成宾语从句。由于汉语不习惯用被动句表达，汉译时往往需要把主句的谓语译成主动语态，并增译泛指性的主语“人们”、“我们”、 “大家”、“有人”等，而把原来的主语从句译成宾语从句。这种译法的特点是保留原文句子结构的前后顺序，先译主句，后译从句。
It is often asked what the mechanism of cancer is.人们常问癌的机理是什么。
It has long been known that the electric properties of semiconductors depend very much on their Parity.众所周知，半导体的电性能在很大程度上取决于它本身的纯度。
It has been roughly estimated that forty per cent of human diseases are the result of infection by bacteria.有人粗略估计，人的疾病有40%是由细菌感染造成的结果。
b）译成并列分句有许多以it作形式主语而谓语是系词（be）加表语的句子，即“it+be+表语+that”结构，可先把主语从句与主句分开翻译，译成第—并列分句，再将主句译成第二并列分句，并在第二分句中增译主语“这”，以起承上启下的作用。这种译法的特点是颠倒原句结构的顺序，先译从句，后译主句。
It is common，sense that a liquid has no definite shape，yet it has a definite volume. 液体无一定形状，而有一定体积，这是一般常识。
It is a matter of common，experience that bodies are lighter in water than they are in air. 物体在水中比在空气中轻，这是大家共有的经验。
c）谓语分译谓语分译是汉译带形式主语it的主语从句的一种常用方法，即先把主句的谓语译成一个独立语，再译从句。
It is true that the high voltage cable would need to have more insulation.的确，高压电缆需要更好的绝缘，-
It is clear that the difference between elements is in the structure of their atoms.很清楚，元素之间的差别就在于它们的原子结构。
二、表语从句
1.英语的表语从句总是位于系词be之后，汉译时顺序一般不变。
The first thing to be sure of is whom science Should serve.首先要明确的是，科学应该为谁服务。
The truth is that men are developed from anthropoid apes.真实情况就是人类是从类人猿进化而来的。
The question was whether it was common cold or influenza.问题是这病是普通感冒还是流感。
2.表语从句在下述四种句型中汉译时可按汉语表达习惯灵活处理，即可先译主句，后译从句；也可先译从句，后译主句。
a）在“That（this）is why…”句型中，如先译主句，后译从句，通常译成“这就是为什么…”、“这就是为什么…的原因”、“这就是…的缘故”等。若先译从句，后译主句，通常译成“…原因就在这里”、“…理由就在这里”等。
That is why they catch cold easily.这就是他们为什么容易感冒的原因。
That is why she is so happy.这就是她这样高兴的缘故。
b）在“This（it）is because…”句型中，通常先主句，后译从句，译成“这是因为…”、“这是因为…的缘故”、“这是由于…的缘故”等。
It is because a conductor carrying a current is surrounded by a magnetic field.这是因为载流导体周围有一个磁场。
This is because people engaged in changing reality are usually subject to numerous limitations.这是因为从事变革现实的人们，常常受着许多限制。
c）在“This is what…”句型中，若先译主句，后译从句，通常译成“这就是…的内容”、“这就是…的”等。若先译从句，再译主句，通常译成“…就是这个道理”、“…就是这个意思”等。
This is what we have discussed in this article.这就考我们在本文中讨论的内容。
This is what is meant by “failure is the mother of success” and aa fall into the pit, a gain in your wit.”所谓“失败乃成功之母”，“吃一堑长一智”，就是这个道理。
d）“It is just as…”句型中，通常先译主句，后从句，译成“这正像……的那样”、“这正如……的那样”等。
It is just as Lowell Ponte stated，“Dead Mixers: Alcohol and Tobacco.”这正如（美）洛厄尔 · 庞特所说的那样：“死亡搅拌机——饮酒又吸烟。”
三、宾语从句
1.用that，what，how，whether，if等引导的宾语从句，汉译时，像宾语的译法一样，一般不需要改变它在原句中的顺序，可进行顺译。
We all know that cigarette smoking is hazardous to health and that alcohol abuse can kill.我们都知道吸烟对人体健康有害，我们也知道不加节制地饮酒能致人f死。
I'm wondering if the heart of all new ideas lies in the borrowing，adding，combining or modifying of old ones. 我想知道：一切创新实质上是不是对旧事物的借鉴、充实、组合或修改。
2.带先行宾语的宾语从句，先行代词it可以省译。
Nutritional experiments have made it evident that vitamins are in dispensable for one's health and growth.营养实验已经证明，维生素是人们健康和成长所不可缺少的。
3.英语中介词in后面跟有宾语从句，这个宾语从句常常可以译成原因状语从句，即用“因为…”、“在于… ”、 “是因为…”等词汉译。
Carbon differs from the metals in that it's resistance decreases as its temperature rises.碳与金属不同，因为温度升高时，碳的电阻降低。
Liquids are different from solids in that liquids have no definite shape.液体与固体的区别在于液体无一定形状。
4.介词except，but，besides，except that等后面的宾语从句，常常译成并列分句，即用“除…之外”、 “除非…”、“此外…”、“只有…”、“但…”等词汉译。
It will go hard but that we shall bring more land under cultivation.除非扩大耕地面积，否则，事情就不好办了。（but是多功能的通用词，这里作介词，后接从句，表示唯一的条件。）
He usually goes to work on his bike except when it rains.除雨天外，他常骑自行车上班（except+宾语从句，=on rainy days）
His account is correct except that some details are omitted.除有些细节未提到外，他的报导是正确的。
注：except that（+从句）多指对非同类事物的排除，表示“说明基本情况后，仅在细节上对主要意思作些修正”。except（+从句）多指对同类事物的排除。
5.宾语从句被特别强调时，常置于译文句首，形成倒装句。
What I have learned from the old scientists I'll never forget.对老科学家面聆的教诲，我将铭肌镂骨。
What the country thinks and worried about we should think and worried about.我们应想国家之所想，急国家之所急。
四、同位语从句
由that引导的同位语从句通常有三种译法：顺译法、倒译法、插译法。由于同位语从句是用来进一步说明或解释其先行词（某些抽象名词如suggestion，desire，fact等）的，故三种译法都与先行词有关；又由于先行词置于主句之中，故三种译法也都与主句有关。现分别简述如下：
1.顺译法
a）先行词和同位语从句相连：
His determination that his son should have a good education is most praise-worthy.他决定其儿子去接受良好的教育是非常值得称赞的。
b）主句和同位语从句相连：主句和同位语之间不加标点、词语，或加“即”、“就是”、 “说”、“他说”、 “他们认为” 、“其内容是”等词来分开。
Andrew had a warm desire that the conversation might continue.安德罗热烈期望继续对话。（主句和同位语从句之间不用标点或词语分开。）
The process of exchange of gases follows a simple law of physics that a gas flows in to the direction of least pressure气体交换过程遵循一条简单的物理规律，即气体向压力最小的方向流动，（主句和同位语从句之间加“即”来分开。）
The name “volcano” indicates the belief of the ancient Greeks that the turning hills of the Mediterranean were the workshops of the divine blacksmith, Vulcan. “火山”这个名称表示古代希腊人的信念，他们认为地中海内许多燃烧的小山都是神匠伐尔肯的工场。（主句和同位语从句之间加“他们认为”来分开。）
For a long time scientists could find little use for the materiel which remained after the oil had been taken out. Then one day the scientists discovered the wonderful thing that it could be turned into plastics.在漫长一段时间科学家不会利用炼油后剩余物。后来，科学家终于发现了一件奇妙的事情，这就是能将炼油剩余物变为塑料。（主句和同位语从句之间加“这就是”来分开）
2.倒译法
a）主句和同位语从句相倒：
There is no possibility that human beings will ever be controlled by robots.人类受机器人控制是不可能的。
So far there is no proof that UFOs or spacesh ps from other planets do exist.究竟有无不明飞行物或来自其他行星的宇宙飞船，迄今尚无法证实。
b）先行词和同位语从句相倒。 译文往往形成三种句型：“同位语从句+这……+先行词”、“同位语从句+的+先行词”、“认为+同位语从句+的+先行词”。
The fact that it was running about in broad daylight was unusual, for these spiders are nocturnal.节肢动物在白昼四处乱爬，这种现象是不常见的，因为这些蜘蛛一般在夜间活动。（“同位语从句+这 ……+先行词”）
The announcement that all flights were cancelled because of bad weather distressed the waiting passengers.由于气候恶劣，撤销全部航班的通知使等候着的旅客们感到十分苦恼。（“同位语从句+的+先行词”）
Now the conventional statement that faster-than-light travel is impossible prevails among us.目前，那种认为“超光速运动不可能”的传统说法在我们中间占优势。（“认为+同位语从句+的+先行词”）
3.插译法
a）先行词和同位语从句相插：
When imaginative scientists first suggested the possibility that one person could speak directly to another over a long distance，few people took them seriously. 当富有想象力的科学家最初提出某人可能同相隔遥远的另一人直接通话时，极少有人认真对待他们。
b）主句和同位语从句相插：译文会出现两种情况——主句集中译；主句分散译。
There were hopes，however, that the problem of the rabbit would become manageable. 但兔子祸患有希望得到控制。（主句集中译）
There is every probability that the fire will spread to the main street.这场火灾大有蔓延到大街的可能。（主句分散译）
There was danger that this rudder would be torn away as well.这个舵也有被卷走的危险，（主句分散译）
练习：试将下列句子译成汉语（注意名词性从句）：
1. What little he said on the subject was full of wisdom.
2.It is not a question how much a man knows but what use he can make of what he knows.
3.They are not prepared even to admit the possibility that noise affects people.
4.The students like to hear the story that a kind tigress has taken care of a baby-child for several years.
5.The idea that continents broke and drifted apart is known as the hypothesis.
6.The experiment made it clear that the second spark was caused by the first.
7.It's generally agreed that the act of developing new ideas involves some five steps：first insight，preparation，incubation，illumination and verification.
8.Remember that almost every innovation came about because a determined person stubbornly believed in his or her imagination.
9.What this means is that virtually all those tasks formerly dependent on man's sight can now be automated.
10.The blunt truth of the matter is that human beings are not designed for tasks which require relentless vigilance: for the sophisticated human brain these are fatiguing and boring.
参考答案：
1.他就是那个问题所发表的一点意见充满智慧。（what引出的主语从句可按原文顺序汉译。）
2.问题不在于一个人知道得多少，而在于他怎样运用他所知的知识。（介词but后接第一个代词what引出的宾语从句，介词of后接系二个代词what引出的宾语从句，应引申才能译好。）
3.他们甚至不愿意承认噪音可能对人有影响。（先行词possibility和that引出的同位语从句插译。）
4.学生们喜欢听那个故事，其内容是一只慈爱的母虎照应了一个婴孩好几年。（主句和同位语从句之间加“其内容是”。）
5.认为大陆曾经断裂并漂离的设想叫做大陆漂移假说。（“认为+同位语从句+的+先行词”）
6.这个实验说明第二个火花由第一个引起。（形式宾语it省译。）
7.（人们）通常认为，创新活动大致包括五个阶段：初步设想、准备、酝酿、萌发、验证。（先译主句，后译that引出的主语从句。）
8.要记住，几乎每一项革新的问世都是由于某个有决心的人坚信自己的想象力的缘故。（that引出宾语从句，顺译。）
9.实际上，这意味着从前所有离不开人的视觉的工作，现在都可以自动化了。（What this means是主语从句，that引出表语从句virtually插译置句首）
10.益而易见的事实是：人体的构造不是为了做那些精神一直要保持高度集中的工作而设计的，因为这些工作会使复杂的人脑疲劳生厌。（先译主句The blunt truth of the matter is，后译由that引出的表语从句。）