根据词根推断词义
英语单词的前、后缀固然很重要，但最重要的是词根，它是词的核心内容，是一个词最根本的、不能加以分析的部分，它揭示词的最根本意义。比如：
port 门，口，携带
port n.港口
porter n.看门人；搬运工
airport n.机场；航空港
heliport(=helicopter+airport)
n.直升机场
transport(trans=from one place to another)
v.运输
显而易见，port是上述一系列单词的词根，词根加词缀可以改变原来的词义或词性，对于主要的词根考生必须逐步记住。只要顺藤摸瓜，许多英语词汇都可以找到其根源(主要是拉丁根源)，再加上为数不太多的常见前后缀，考生就能很快掌握和熟悉英语词汇。
例1.(1994年考题第4篇66题)
With as many as 120 varieties in existence, discovering how cancer works is not easy. The researchers made great progress in the early 1970s, when they discovered that oncogenes, which are cancercausing genes (基因),are inactive in normal cells. Anything from cosmic rays to radiation to diet may activate a dormant oncogene, but how remains unknown. If several oncogenes are driven into action, the cell, unable to turn them off, becomes cancerous.
The word "dormant" in the third paragraph most probably means _____ .
［A］ dead
［B］ everpresent
［C］ inactive
［D］ potential
解答该题既可以利用构词法，也可以利用上下文相关内容。根据词的构成，我们知道"dorm"是该词的词根，等于"sleep"，如：dormitory(寝室，宿舍)，dormicive(安眠的，安眠药)，在原文中，"dormant"与上句的"inactive"是同义词；"active"为"活跃的"，加前缀"in"(不；反；非)表示"潜伏的，不活跃的"，恰好与"dormant"(休眠的，蛰伏的)同义。
例2.
The fact that some naturally lefthanded children are forced into becoming righthanded may even result in levophobia. Sufferers from this rare condition find their hearts pound as if a heart attack were coming on as a result of their brains releasing adrenalin(肾上腺素) at the mere prospect of a leftoriented maneuver. They refuse to stand on the left side of an elevator, make lefthand turns when driving, sometimes even to look to the left. Psychologists believe levophobia will only disappear entirely when lefthanded children--a minority in all known society--are fully accepted
The word "levophobia" in the reading means most nearly
［A］ a look to the left
［B］ an irrational fear of the left
［C］ a problem caused by attitudes
［D］ heart attacks
全文谈论的是要想叫左撇子做事的改用右手，会出现什么结果。抛开文章不看，只根据构词来识别"Ievophobia"，就不难找出答案。词根"levo"表示"左，向左"，例如：levo cardiogram(左心电图)或levogram; levoratation(左旋)。词根"phobia"表示"fear, dislike"(怕，厌恶)，如：zoophobia(动物恐怖症)：photophobia(怕光，畏光)等。把"levophobia"两部分的词意加在一起，就是"左侧恐怖症"，选择项B(一种对左的不合情理的恐惧)无疑与上述分析所得的意义相似，故为正确答案。
此外，我们还可以通过其他方法获得同一答案：文章一开始交待"强使一些生来就惯用左手做事的孩子改用右手，可能会使它们产生一种‘levophobia'"，接下来谈这种少见病的患者......一想到左向活动(at the mere prospect of a lefthand maneuver)就会...，以至于乘电梯时，他们不肯站左边，驾驶车辆时，他们拒绝左拐弯，甚至refuse to look to the left.贯穿全文的中心都是与这种左侧恐惧症有关，这样，我们再根据四个选择项的意义就可以找出正确答案。