托福听力考点信号词
许多考生在进行托福听力备考的过程中经常会有一种感觉就是学术讲座(lecture)的信息量较多，无法完全在短短的2-3分钟时间内记录下所需要的关键线索。
01解释说明类(Explanatory)信号词
常见的有同意替换和举例说明
同义替换，常见的信号词有
1. that is to say；
2. namely；
3. or rather；
4. to be more exact；
5. to put it another way；
6. in other words；
7. by definition .
在托福听力中，我们经常会听到进行定义介绍的说法如“it is called/it’s known as + 专有名词”， 或者“专有名词 define/refer(s) to …”。一般而言，这类专有名词术语某个特定的领域，如商业、教育学、考古学、地球科学。考生相对不太熟悉，因此这些信号词的前后内容能够增加考生对整体听力讲座的把握和主旨理解。
例：
According to this theory, an organism’s cells in their regular metabolic processes, by metabolic processes I mean things like cellular restoration and reproduction. Uh, in their regular metabolic processes cells generate oxygen molecules, some of which have an extra electron. That extra or free electron makes the whole molecule unstable. The unstable molecule is known as a free radical. Okay? And according to this theory these free radicals causes damage to other molecules and structures within the cell, including most significantly to the cell’s DNA. And it’s this gradual degradation of DNA and tissues and larger structures that drives the aging process.
文中用到了be known as 的结构给专有名词自由基下了定义
例：And finally, cephalopods also use what’s called disruptive coloration. Disruptive body patterns are irregular patches of different shapes and colors that serve to distract an observers attention and obscure the outline or crude shape of the animal. In other words, a disruptive pattern makes it difficult to see the shape and size of the animal. Disruptive patterns can also achieve some level of general resemblance to the background. That is they often contain small regions of model patterns or even uniformity.
In other words 换言之，同意替换，说上句和这句说的是同一个东西。
02举例说明的信号词
托福听力中，教授也常会进行举例说明
常见的举例信号词：
1. for example；
2. as；
3. for instance；
4. Like；
5. Say .
通过举一些常见或者比较容易理解的例子，去解释某样事物或某个现象，使得其更加生动形象，通俗易懂。
例：
Roman pottery for example, it was typically glazed so it’s very shiny, easy to see against the soil. But, pottery of the early middle ages was brown or grey and it wasn’t glazed, so you’d have trouble spotting it at an excavation. It’s kind of camouflaged against the soil. So it’s easy to draw the wrong conclusions about population size based on the available evidence.
例子中提到了pottery的例子，对比了罗马时期和中世纪早期的pottery的区别，例证的提示词用到的是for example
例：
Professor: Yes, and Wright was intent on creating effects like that. Another example. I mentioned the stone floors, those floors have an uneven textured surface. They’re waxed and highly polished so they’re shiny and reflective. This achieves an intriguing effect. Inside the house it actually looks as though there’s moving river water running over the floor stones.
这是一篇介绍建筑学家作品的讲座，讲的是wright 的falling water 落水山庄。
截取片段中提到了Wright在创作落水山庄时所用到的自然理念，其中用了stone floor的例子来营造出河流的景象。例证提示词用的是 another example。
03逻辑性信号词
如最常见的原因、对比、转折、并列等。对于原因信号词，考生可以尤为注意
1. because (of)；
2. so；
3. the reason why；
4. since；
5. as/for .
例：
Now all of this may not seem relevant to this week’s reading about the ancient Mayan populations in Central America, which we’ll get to in a minute. But, you’ll notice that your book includes population distribution maps that have been generated based on archeological evidence. So, a word to the wise, population distribution maps for western Europe show lots of large empty spaces for the early Middle Ages even though evidence, like those post holes and documents about Yeavering, might tell quite a different picture.
书中的玛雅文明中的人口分布图，但是是根据考古证据绘制的，所以（SO），尽管Yeavering的考古证据会得出不一样的结论，但是对比中世纪早期的西欧人口分布地图，依然有很多空白。表明了考古证据并不是显示该地人口分布的决定性因素，有时候人们的生存痕迹并不一定能够保存下来。
04对比信号词
对于对比信号词，考生除了注意比较级和最高级之外，还要多注意类比和对比
1. compare to；
2. different from……l；
3. unlike……；
4. (not) as ……as .
等这些间接表达对比的词或词组。
例：
Graphene is the strongest material ever made. Its strength is due to its perfect crystal and atomic structure, which looks like chicken wire under a microscope actually. You could compare graphene to diamond because they’re both made of carbon atoms that are arranged in a simple and regular pattern. But unlike diamond, graphene is incredibly flexible akin to plastic wrap. And because of its atomic structure, graphene is also an outstanding heat conductor. Electrons speed through this material much faster than they can through other materials.
石墨烯是有史以来最坚固的材料。它的坚固是由于它完美的晶体和原子结构，在显微镜下看起来像铁丝网。在介绍石墨烯的时候通过类比钻石来进一步说明了它的柔韧性和导电性。
05转折信号词
这些是考生尤其应该注意的信号词。即教授最终想要强调的点，也是高频考点的地方。通过先陈述一部分事实或者抛出一个问题，然后来一个转折性的连词，提出真正的观点。因此这些转折词前后信息是考生必须要注意的地方。
转折信号词是托福听力中最常见的信号词之一。常见的信号词形式如下：
1. however；
2. nevertheless；
3. yet；
4. still；
5. though；
6. anyhow；
7. even so；
8. in any case；
9. anyway；
10.after all；
11. in spite of that；
12. by the way .
例：
But there’s another challenge, the industrial production of graphene sheets. The adhesive tape method is good for producing small samples for research purposes but we need a reliable way to mass produce graphene in large sheets so it can be sold to companies that manufacture transistors for example.
在讲解石墨烯的这篇讲座当中，教授先讲了石墨烯的各种性能优势，随后but画风一转讲到了在应用上的面临的问题和挑战。
06并列信号词
1. first；
2. second；
3. third；
4. for a start；
5. for one thing；
6. for another；
7. to begin with；
8. next；
则是很好的信号词，提示了两句句子之间的平等并列关系。
A synthesizer can generate new sounds and then combine them in symphonic ways. It can mimic the sounds of conventional instruments as well as create the synthase tones. And the second thing it can do is modify sound.
这篇音乐发展历史的讲座，教授讲了合成器。
一方面不仅可以产生生的声音
另一方面还可以修改声音
