The polyphonic and polysemous Chinese characters in modern Chinese mostly originated from the derivations by sound-change in classical Chinese .Since B .Karlgren first focused his attention on the existence of large groups of cognate words in classical Chinese in his Word Families in Chinese (1934),efforts have been made to find the semantic relationship that corresponds to the phonetic contrasts in the philological explanation for lexical meaning,grammatical function and morphology .Based on previous researches,this study selects Zhong (middle,“中”) and Jian (space,“间”) as two samples,and attempts to examine their derivational processes,to reveal their complicated relationship of sounds,meanings and the shapes of Chinese characters in the development of Chinese language,which can not only enrich the research in the polyphonic and polysemous Chinese characters in modern Chinese,but also contribute to the compilation and revision of Chinese dictionaries . The varia lectio (异读) data of this paper are mainly from Jingdian Shiwen (《经典释文》) and Syllabary of Dialect Pronunciations of Chinese Characters (《汉语方音字汇》) . Jingdian Shiwen is rich in derivations by sound-change from Pre-Qin period to Wei and Jin dynasties,and has experienced the stage of the morphological decline,while Syllabary of Dialect Pronunciations of Chinese Characters is well acclaimed for its colloquial features .The combination of these two helps examine the origin,development and decline of the derivations by sound-change of Zhong and Jian . The derivation by sound-change of Zhong goes as follows :(1) Basic form (原始词),even tone (平声),unvoiced initial (清声母),means″middle ; fair and equitable rule,″noun ; (2) Derived formⅠby tone-change to falling tone(去声),unvoiced initial,means″in the middle of,″ adjective ;(3) Derived formⅡby meaning-change,falling tone,unvoiced initial,means″to meet the standard ;to hit the target,″verb ;(4) Derived formⅢby initial-change,falling tone,voiced initial (浊声母),means″just in the middle of,″adjective . The derivation by sound-change of Jian goes as follows :(1) Basic form,even tone,unvoiced initial,means″space between,″noun .(2) Derived formⅠby meaning-change,even tone,unvoiced initial,means″to await a favorable opportunity,″verb .(3) Derived formⅡby initial-change,even tone,voiced initial,means″to be leisured,″adjective .(4) Derived formⅢ by tone-change,falling tone,unvoiced initial,means″to be or place between ;to sow discord,″verb . According to the shapes of Chinese characters,Zhong and Jian represent two kinds of form changes in the development of Chinese language . Zhong represents the direction in which the original form has been maintained,while Jian represents the other direction where the form has changed .The basic form of Jian was initially written as“閒”,and then replaced by the popular shape“间”,and its derived form borrowed another shape“闲”. In Syllabary of Dialect Pronunciations of Chinese Characters,both Zhong and Jian are still polyphonic and polysemous in 20 dialects,which should be the last vestiges of derivations by sound-change in classical Chinese . The study concludes that in the medium-sized philological dictionaries,such as Modern Chinese Dictionary (《现代汉语词典》),Xinhua Dictionary (《新华字典》),the synchronic sound,meaning and shape of polyphonic and polysemous Chinese characters can be marked according to their usages in modern Chinese,while in the large-scale philological dictionaries,such as Chinese Dictionary of Etymology (《辞源》) and Great Chinese Dictionary(《汉语大词典》),the diachronic sound,meaning and shape of polyphonic and polysemous Chinese characters should be marked according to their corresponding relationship in the development of the Chinese language,which is a goal that the compilation and revision of philological dictionaries should achieve in the future .