在记忆和背诵考研单词时，老师们会推荐词根词缀法记忆单词，这种方法科学合理，记忆牢固并且迅速。同时，我们都知道，词汇的前缀一般修饰或者改变单词的意思，词汇的后缀一般改变单词的词性。万学海文为了广大考生更好更快的记忆单词，对考研英语词汇常见的反义否定前缀进行了汇总，希望对2018年考研的广大考生有所帮助。

　　1. dis-(加在名、形、动词前)表示“不，不再”

　　disadvantage n. 不利，不利条件;

　　E.g. Depression is the third thing that works to my patients' disadvantage.

　　抑郁是威胁我的病人健康的第三大杀手。

　　disappear. v. 消失

　　E.g.He saw something dark disappear behind the curtain of leaves.

　　他看到一个黑漆漆的东西从浓密的树叶后消失了。

　　disconnect. v. 分离

　　E.g.You should disconnect the wireless set before you make adjustments inside it.

　　你应先拔掉无线电插头,再做内部调整。

　　2. di-,dif-, dis-：away，negative否定，分开，不

　　distrust. v. 不信任, 怀疑

　　E.g.What he saw there left him with a profound distrust of all political authority.

　　他在那儿的所见让他对一切政治当局产生了一种深深的不信任感。

　　disassemble v. 拆开

　　E.g.We had to completely disassemble the engine to find the problem.

　　我们只好把发动机全部拆开以寻找故障原因。

　　differentiate v.区分

　　E.g.A child may not differentiate between his imagination and the real world.

　　儿童可能无法将自己的幻想与真实世界区分开来。

　　3. il-：(加在以“l”开头的词前)表示“不”

　　illiterate n. 文盲;

　　E.g.Many senior managers are technologically illiterate.

　　许多高级经理都对技术知之甚少。

　　illegitimate a. 非法的

　　E.g.The election was dismissed as illegitimate by the opposition.

　　反对党以不合法为由拒绝接受选举结果。