1. A method for generating derivative words, the method comprising the steps of: 1) creating a plurality of derivative grammar rule arrays, each of which comprising a suffix alphabetic character set and a condition array whose condition the base words have to meet, said condition array having a part of speech of the base words as required by corresponding suffix alphabetic character set; 2) inputting a user character set; 3) matching the user character set with each derivative grammar rule array, then obtaining the derivative grammar rule array which matches with the user character set; 4) obtaining a word meeting the requirement of the condition arrays of the obtained derivative grammar rule arrays, from a language database in accordance with the user character set; generating a derivative word via adding the suffix alphabetic character sets to the obtained words, the alphabetic character sets being included in the derivative grammar rule arrays which include the condition arrays as met by the obtained words.