周德清（1277-1365）《中原音韻》韻譜自注：「正語之本，變雅之端」，本文從這兩句切入，以〈正語作詞起例〉為論述文本。又根據周德清所說「呼吸言語之間，還有入聲之別」的立足點，探索周德清「正語」理論之建構。本文分四節。第二節「正語概念的形成與總綱」，闡釋「正語之本，變雅之端」的戲曲背景與涵義。這兩句意謂《中原音韻》既是中原之音的正聲，堪可辨正與《廣韻》之差異，亦可做為矯正方音之病的根本；也是辨別北曲與宋元戲文等其他腔調劇種戲曲語音差異的依據。第三節「正語之本—辨正《中原音韻》與《廣韻》的差異」分別從《中原音韻》平聲分陰平、陽平，入派三聲，無閉口入聲及押韻現象等進行論述。第四節「變雅之端—辨正諸方語之病」，分析周德清「正音」的對象，主要針對宋元戲文載體的吳語。周德清以《中原音韻》與《廣韻》讀音之差異，落實「正語之本」的宗旨；又以中原之音對比吳語或各地方音，落實「變雅之端」的旨趣。對於《廣韻》一書時而偏激，視為鴃舌；時而認同，據以辨明古今字，或據以釋疑字樣，以為指迷。對於方音，視為語病；卻又認同約定俗成的四海之音。究其成書宗旨，則在通古今音變，立戲曲正音。

Zhou Deqing's (1277-1365) Zhongyuan yin yun annotates that his book serves as “a model for zhengyu and a rectification of bianya.” Based on this statement, this article will explore his Rules for Composing the Traditional Northern Opera with Correct Sounds in the book. In addition, according to Zhou's understanding of "entering tones are situated between breathing and speaking,” the author will investigate Zhou's construction of zhengyu theory. This article is divided into four sections. After an introduction in section one, section two explicates the linguistic background and meaning of the above mentioned statement. This statement signifies that the pronunciation in Zhou’s book was deemed standard in the Central Plains, rectifying the disadvantages of various dialects, and differentiating divergences among Guang yun and various types of operas in Chinese dialects. Section three compares the following rhyming phenomena: level tones divided into voiceless and voiced level tones, entering tones recategorized into level, rising, and departing tones, and a lack of closed entering tones and rhyming. Section four analyzes the subject dialects that Zhou rectified, especially the Wu dialect in Song-Yuan southern drama. Grounded in the differences between Zhongyuan yin yun and Guang yun, Zhou fulfilled the objective of “a model for zhengyu” and brought the aim of “a rectification of bianya” to a successful conclusion through the comparison of central pronunciation with the Wu and other dialects. Not completely agreeing with what Guang yun argues, he viewed dialects as having deficiencies and meanwhile accepted them as pronunciation in common practices. His goal of composing Zhongyuan yin yun was to historicize the changes of sounds and therefore normalize pronunciation for traditional Chinese opera.