语法是雅思考试的奠基石，小编今天给大家分享的是语法中“同位语及同位语从句的表示法和判别”。祝大家都能考取理想的分数~
在某一句子成分后面有另外的词、短语或从句(同位语从句)对该成分作进一步说明，在语法上又处于同一地位(即作同一个成分)，称为同位语。
1. 同位语在所说明的句子成分之后，其间没有逗号
Unlike oxygen, the element nitrogen is not active. 与氧不同，元素氮不活泼。 nitrogen 是 the element 的同位语
In today’s China, we returned students are able to do what we could not do before. 在今日的中国我们归国留学生能做过去不能做的事情。 returned students 是 we 的同位语
2. 同位语前后有逗号、冒号或破折号
Yesterday they each saw Dr.Fang, a senior engineer. 昨天他们各位都见到了方博士，他是一位gao级工程师。 a senior engineer 是 Dr.Fang 的同位语
We all have a common desire - to realize the four modernizations in China. 我们都有一个共同的愿望——在中国实现四个现代化。不定式短语作同位语：to realize the four modernizations是 desire 的同位语
3. 用 or 引出同位语
The boiling temperature, or boiling point, is the temperature at which a liquid boils under ordinary pressure. 沸腾温度即沸点，系液体在常压下沸腾的温度。 boiling point 是 boiling temperature 的同位语
The energy of electric current, or of electricity in motion, may be converted to any other form of energy. 电流的能量即动电的能量，可以转化为任何其它种能量。 of electricity in motion 是 of electric current 的同位语
4. 用 such as 或 as 引出同位语
Some building materials such as cement and reinforcing bars are widely used in capital construction. 某些建筑材料，例如水泥和钢筋，广泛使用于基本建设中。 cement and reinforcing bars 是 building materials 的同位语
Plastics as a class are not suitable as materials to carry heavy structural loads. 塑料作为一类材料，并不适于作承受重型结构负荷的材料。 这句里需要注意的是第1个 as 引出同位语，而第二个 as 则引出主语补足语。 a class 是 plastics 的同位语
在线雅思培训：阅读核心词汇表及记忆方法建议
5. 用 of 引出同位语(of 前常是一个概括的名称，of 后是具体的东西或具体数值)
This automobile is running at a speed of 70 miles an hour. 该汽车正以每小时 70 英里的速度行驶。 70 miles an hour 是 a speed 的同位语
He worked in the city of Tianjin two years ago. 两年前他在天津市工作。Tianjin 是 the city 的同位语
6. 用 namely, for example, including, particularly, that is (或 i.e.) 等引出同位语
We have only one way of solving the difficulty, namely, to rely on our own efforts. 我们只有一条解决困难的途径，即依靠自己的努力。 to rely on our own efforts 是 one way of solving the difficulty 的同位语
I want to visit these modern factories, especially the one where you work. 我想参观这些现代化的工厂，特别是你工作所在的那个厂。 the one 是 modern factories 的同位语
同位语从句一般用 that, whether, what, which, who, when, where, why, how 等词引导，常放在 fact, news, idea, truth, hope, problem, information, wish, promise, answer, evidence, report, explanation, suggestion, conclusion 等抽象名词后面，说明该名词的具体内容。换言之，同位语从句和所修饰的名词在内容上为同一关系，对其内容作进一步说明。
1.that 引导同位语从句，同位语从句意义完整(that 不充当任何成分，只起连接作用，不可省略)
The general gave the order that the soldiers should cross the river at once. 将军下达了战士们立即过河的命令。 解析：the soldiers should cross the river at once 是 the order 的全部内容。
2.whether 引导同位语从句同位语，从句意义不完整(if 不能引导同位语从句)
We'll discuss the problem whether the sports meeting will be held on time. 我们将讨论运动会是否会如期举行的问题。解析：the sports meeting will be held on time 意义不完整，应加“是否”的含义才能表达 the problem 的全部内容。
3.when, where, how 等词引导同位语从句，同位语从句意义不完整
I have no idea when he will be back. 我不知道他什么时候才能回来。 解析：he will be back 意义不完整，应加“什么时候”的含义才能表达 idea 的全部内容。
I have no impression how he went home, perhaps by bike. 我不记得他是怎么回来的，也许是骑自行车。 解析：he went home 意义不完整，应加“如何”的含义才能表达 impression 的全部内容。
4.当主句的谓语较短，而同位语从句较长时，同位语从句常后置。
The thought came to him that maybe the enemy had fled the city. 他想到可能敌人已逃离这座城市。 解析：maybe the enemy had fled the city 是 the thought 的同位语从句。
