课堂话语是教学活动发生的主要载体，也是我们研究教学活动的重要抓手。现有研究偏重于课堂话语数量、形式特征的描述，对课堂话语教学意义的挖掘相对缺失，对话语所反映的教学过程及教学机制的分析相对笼统、浅薄。科学语言表达能力是初中数学教学的重要目标，反映了学生抽象逻辑思维的发展水平。科学语言的教学与科学知识的教学、科学思维的发展具有不可分割性，在初中数学教学中需要着重培养学生的科学语言的表达能力，通过有针对性的课堂话语策略引导学生实现语言表达的规范。基于此，本研究从科学语言表达能力培养的视角切入，分析初中数学课堂的教师讲授话语和师生互动话语，总结课堂话语的特点和策略，探究课堂话语对培养科学语言表达能力的作用。

本研究选取了20节优质初中数学课的课堂录像，对课堂话语的特点和策略进行总结与分析。在课堂话语特点的分析部分，根据“序列-话轮-话步”三层级话语分析框架和话语编码表，对课堂话语转录形成的文本进行层级划分和编码，统计话语序列主题、话轮长度和话步类型，总结话语特点，分析其对学生科学语言表达能力的作用。在课堂话语策略的分析部分，根据话语策略分析框架，对指向不同科学语言表达能力教学效果的话语策略进行总结，分析其对学生科学语言表达能力的作用。

研究发现，初中数学课堂话语呈现三个水平的特点：话语序列主题与教学环节对应，序列内师生互动话语多于教师讲授话语；话轮长度长于三段式话轮，受到跟进话步的有无和开放性强弱的影响；跟进话步类型丰富，以总结完善类和要求辩护类为主。这些特点有助于增加学生的表达机会，在完善表达形式和深化话语互动中规范学生的科学语言表达。初中数学课堂话语包括四种策略：发起核心话轮和从属话轮，明确科学概念，提高学生科学语言表达的准确性；使用要求辩护类、重构类、总结类跟进话步，补足句子成分、规范修饰词、调整词序，提高学生科学语言表达的完整性和简洁性；进行讲授或发起互动话轮，进行科学语言形式互换，提高学生科学语言表达的灵活性；发起互动话轮，进行自然语言和科学语言的互译，提高学生的科学语言理解能力，为科学语言表达奠定基础。

研究建议，指向科学语言表达能力培养的课堂话语应有以下要点：增加延长话轮，为学生的科学语言表达创造机会；丰富跟进话步的类型，对学生的科学语言表达进行补充和完善；通过讲授或话语互动明确科学概念和语法，提高语言表达的规范程度；在互动话轮中加强语言互换和转译，提高语言表达的灵活程度。

Classroom discourse is not only the main carrier of teaching activities, but also an important starting point for researchers to explore the teaching activities. Related research focuses on the description of the quantity and formal characteristics of classroom discourse, the mining of the teaching meaning of classroom discourse is relatively missing, and the analysis of the teaching process and teaching mechanism behind classroom discourse is relatively shallow. Scientific language expression ability is an important goal of mathematics teaching in junior middle school, which reflects the development of students' abstract logical thinking. The teaching of scientific is inseparable from the teaching of scientific knowledge and the development of scientific thinking. In junior middle school mathematics teaching, teachers need to focus on cultivating students' expression ability of scientific language, and guide students to realize the standardization of language expression through targeted classroom discourse strategies. Based on this, from the perspective of scientific language expression ability cultivating, the research analyzes  mathematics classroom discourse in junior middle school, summarizes the characteristics and strategies of classroom discourse, and explores the role of classroom discourse in cultivating scientific language expression ability.

The research selects 20 classroom videos of high-quality junior middle school mathematics classes to summarize and analyze the characteristics and strategies of classroom discourse. In the characteristics analysis, based on the three-level discourse analysis framework and the discourse coding table, the research divides and codes the text transcribed in classroom discourse, describes the theme of discourse sequence, the length of discourse exchange and the type of discourse move, summarizes the characteristics of classroom discourse, and analyzes its effect on students’ scientific language expression ability. In the strategies analysis, based on the discourse strategy analysis framework, the research summarizes the discourse strategies pointing to different teaching effects of scientific language expression abilities, and analyzes its effect on students’ scientific language expression ability.

The research finds that the mathematics classroom discourse in junior middle school presents the following characteristics on three levels: Discourse sequences are arranged in the order of the instructional design. The interactive discourse between teachers and students in the discourse sequence is more than that taught by teachers. The length of exchange is longer than triadic dialogue, which is influenced by the openness of follow-up moves. There are many types of follow-up moves, including summary, praise, supplement and request for clarification.  These characteristics are conducive to increasing students' expression opportunities and standardizing students' scientific language expression in standardizing expression forms and deepening discourse interaction. Junior middle school mathematics classroom includes four  discourse strategies: Initiate core exchanges and dependent exchanges, and clarify scientific concepts, in order to improve the accuracy of students' scientific language expression. Use request for clarification move, reconstruction move and summary move, supplement the sentence components, standardize the modifiers and adjust the word order, so as to improve the integrity and conciseness of students' scientific language expression. Give instruction or initiate interactive exchanges, transfer one scientific language form into another, in order to improve the flexibility of students' scientific language expression. Initiate interactive exchanges, translate natural language into scientific language, or translate scientific language into natural language, in order to develop students' scientific language understanding ability, which is the foundation of scientific language expression ability.

The research comes up with the following suggestions for classroom discourse with the teaching aim of develop students’ scientific language expression ability: Increase and prolonging exchanges to create opportunities for students' scientific language expression. Enrich the types of follow-up moves to improve the students' scientific language expression. Clarify scientific concepts and grammar through teaching or discourse interaction, and improve the standardization of language expression. Strengthen language exchange and translation in exchanges to improve the flexibility of language expression.