大家知道，托福阅读备考是个长期的过程，在前期词汇的积累过程中，令各位宝宝头疼的不仅仅是像exuberance，centrifugal这样的长单词，一些小词也同样困扰着我们，比如as这个词，它的无所不在及意思繁多就给我们理解句子带来很多麻烦。今天我们就来简单的总结一下这个小连词在托福阅读中的作用，注意啊是托福阅读，如果你想了解它的全部意思，请参考牛津词典，朗文词典，韦氏英语词典...
01一个数字标题
as做连词(连接句子)主要的有两个用法：
1) 做时间状语从句，表示随着.../当...时候，相当于when
eg. As the new markets created fortunes for the few, the factory systemlowered the wages of workers by dividing labor into smaller, lessskilled tasks. (摘自OGArtisansand Industrialization)
随着新市场为少数人创造了财富，工厂体系通过将劳动力分成更小、技能更低的任务，降低了工人的工资。
Asoil becomes increasingly difficult to find, the search for it isextended into more-hostile environments. (摘自tpo4PetroleumResources)
随着石油越来越难找到，对它的搜寻也延伸到了更恶劣的环境中。
2)做原因状语从句，表示由于，因为，相当于because
eg. Until the 1970s, it was widely assumed that Chaco had been a forestedoasis that attracted farmers who initially flourished but eventuallyfell victim to their own success and exuberance, as they denuded the canyon of trees and vegetation to build large greathouses. (摘自真题ChacoPhenomenon)
直到20世纪70年代，人们普遍认为Chaco是一片森林覆盖的绿洲吸引了不少农民，他们起初很繁荣，但却沦为自己的成功和繁荣的牺牲品，因为他们砍伐了峡谷中的树木和植被来建造了巨大的房屋
Certainly,rational appeals in advertising aimed at children are limited,asmost advertisements use emotional and indirect appeals topsychological states or associations.(摘自tpo14Childrenand Advertising)
当然，在针对儿童的广告中，理性诉求是有限的，因为大多数广告都是对心理状态或联想的情感诉求和间接诉求。
02一个数字标题
as做介词的时候，后边跟名词或v-ing的形式，表示“作为”
eg.Of158 stencils in the French cave of Gargas, 136 have been identifiedasleft,and only 22 asright;right-handedness was therefore heavily predominant.(摘自tpo12WhichHand Did They Use)
在法国加加斯洞穴的158个模板中，有136个被认为是左边的，只有22个是右边的;因此，惯用右手的人占绝大多数。
Sociologistsview primary groups asbridgesbetween individuals and the larger society because they transmit,mediate, and interpret a society's cultural patterns and provide thesense of oneness so critical for social solidarity.(摘自tpo13Typesof Social Groups)
社会学家认为，主要群体是作为个体与大社会之间的桥梁，因为它们传播、调解和解释社会的文化模式，并提供对社会团结至关重要的统一性。
03一个数字标题
关系代词这个名字只有在定语从句中才有。当as出现在定语从句中时，往往做的是非性从句，指代前边一句话或者一件事，表示“正如,就像”
eg.whydid they not discover the geometric perspective as European artists did in the Renaissance?(摘自tpo11AncientEgyptian Sculpture)
为什么他们不像欧洲文艺复兴时期的艺术家那样发现几何角度呢?
Filtering seawater for its particulate nutritional content can be anenergetically demanding method of feeding, particularly when thecurrent of water to be filtered has to be generated by the organismitself, as is the case for all planktonic animals. (摘自tpo45 FeedingStrategies in the Ocean)

过滤海水的微粒营养成分可能是一种需要能量的喂养方法，特别是当需要过滤的水流必须由生物体本身产生时，就像所有浮游动物一样。
当然，as的具体意思还有很多，这里总结的只是在托福阅读中常见的三种形式：连词，介词和关系代词。还有一个小小的技巧，就是平时记这样的小词多记它的语境，比干背它的用法要容易很多。