【正确答案】Back-formation refers to an unusually abnormal type of word-formation where a shorter word is derived by deleting an imagined affix from a longer form already in the language．For example, editor/edit, enthusiasm/enthuse．

【答案解析】[解析] 本题考查构词法中逆构词法概念，考生应能灵活掌握其他类型的构词法，如新创法，混成法，缩写词，缩略语，类推构词及借词等。