1. that is to say;
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。
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
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。
1. for example;
3. for instance;
5. Say .
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.
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。
1. because (of);
3. the reason why;
5. as/for .
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.
1. compare to;
2. different from……l;
4. (not) as ……as .
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.
7. even so;
8. in any case;
11. in spite of that;
12. by the way .
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.
4. for a start;
5. for one thing;
6. for another;
7. to begin with;
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.