先来看下面这段话：
Panda bear is a kind of docile lovely animal in the southwest of China. Its cherubic appearance and awkward movement appeals to not only children but also adults. It symbolizes the spirit of peace and harmony, which is cherished by Chinese people. Expansion of human activities to wild areas has caused a sharp decrease in the number of panda bears.
这段话由四句组成，彼此之间存在着明显的联系，论证的都是中国大熊猫的情况。排除语法，文字优美等诸多考虑，这段话给人的感觉是四个孤立的句子，而不是一段文章。
其原因之一，是它缺乏必要的过渡(Transitions)，文中主题之间缺乏有机联系导致文章缺乏必要的连贯性。这一问题也是学生在写作实践中普遍存在的现象。
在诸多北美考试的写作评分标准中，都出现过与连接和过渡相关的要求，比如
*"displays unity, progression, and coherence, though connection of ideas may be occasionally obscured" (iBT Independent Writing 3分评分标准)
*"develops and organizes ideas satisfactorily but may notconnect them with transitions" (
*"is limited in its organization or focus, or may demonstrate some lapses in coherence or progression of ideas" (Sat Write an Essay 3分评分标准)
各种考试中不约而同的出现对于coherence，connection，transitions等概念的要求，这三个词的翻译为"连贯性"，"连接"和"过渡"，而connection和transitions在这里可以被理解为同义词，而且这部分做的不到位都会影响考试写作部分的成绩，其重要性可见一斑。
那么到底甚么是Transitions呢?
在GRE考试中又被称作Transitional devices，连接元件，是出现在文章中的一种词，短语甚至句子，其目的是用来表明它前后两部分之间的逻辑关系的，它的用处是能够帮助读者自然地从作者的一个idea转移到下一个idea，使用的结果可以使文章的逻辑性更强，更加连贯。
打个比方来说，它很像道路上引导旅者的标志牌(They are like the road signs that guide travelers-College Writing Skills)。之所以说"前后两部分"，是因为Transitions的前后可能是两个段落，两句话，甚至两个单词，它们彼此之间都会存在各种各样的逻辑关系，比如说：
*Addition: and, in addition, additionally, one, another, first of all, secondly, furthermore, moreover
*Time: then, after, before, since, once, until, meanwhile, now, during
*Space: next to, across, above, below, nearby
*Change-of-direction: but, yet, however, otherwise, nevertheless, although, in contrast, on the contrary
*Conclusion: because, so, therefore, as a result, consequently, thus, in summary, conclude
这种transitions的出现方式非常多样，包含了很多词性：连词，介词，副词，动词等等，还有很多短语，所以把它称之为Transitional devices是非常恰当的。
在写作文章中充分合理地加入这种Transitional devices，就可以在很大程度上增加文章的连贯性，比如还是本文开头的那段话，稍加修改之后变成了：
Panda bear is a kind of docile lovely animal in the southwest of China. Because of its cherubic appearance and awkward movement, it also symbolizes the spirit of peace and harmony, which is cherished by Chinese people. However, expansion of human activities to wild areas has caused a sharp decrease in the number of panda bears.
通过判断，我们发现修改前的一二两句之间存在因果关系，因此加入because of 将它们连在了一起;而修改前的第三句和前两句之间是一个并列关系，因此加入了also;最后一句话的意思和前面明显出现了转折，通过however来体现这种转折关系。经过修改之后，几句话被有机地结合在了一起，形成了一段篇章而非四个独立的句子。
不过，在充分使用各种连接语的同时，也应该注意不同词性连接语的用法，比如连词很自由，and，but，so这些连词的后面可以跟名词或者句子。但是介词(介词短语)后面只能跟名词，比如because of， instead of，in addition to等等;而副词(副词性短语)的后面只能加句子，比如however, in addition, as a result等等。
掌握gre作文连接词是大家在备考