1．un-,常接动词、形容词、副词.
如：uncover,uncork,undeniable（无可否认的,确实的）,uncommon,unexpectedly
2．in-,常接名词、形容词、副词.
如：inability,incoherent（思想不连贯的）,independent,inactively
＊以un-开头的单词否定形式,若是形容词,则其名词通常为in-开头.
如：unable→inablity uncivil（不礼貌的）→incivility
3．im-,常接以b、m、p开头的单词.
如：imbalance,impartial（公正的,不偏袒的）,impatient,impolite,immobile（不能动的）
4．il-,常接以l开头的单词.
如：illegible（难读的,不清楚的）,illiterate（不识字的）
＊但不绝对,如disloyal,loyal以l开头,加的是dis-前缀.
5．dis-
如：disadvantage,disagree,disconten（不满意的）,discover,dissimilar
6.a-,数量较少.
如：aseptic（无菌的）,atheism（无神论）
7．ab-,数量更少.
如：abnormal（不正常的）
练习：你知道下列单词的否定形式吗?
rational perfect logical fold certain convenient effective harmony honest regular sexual sincere responsible modest comfortable mature satisfy appear pure avoidable accurate legal
答案：irrational imperfect illogical unfold uncertain inconvenient ineffective disharmony dishonest irregular asexual insincere irresponsible immodest uncomfortable immature dissatisfy disappear impure unavoidable inaccurate illegal
