史蒂芬C．莱文森在他的《语用学》一书中把会话定义为：“两个或两个以上的人进行自由交流的一种谈话方式，一般不包括这样一些特殊的场合，象宗教仪式、法庭、教室以及类似的环境”．会话是说话人在共同的环境下为了一定的目的而进行交流的一种形式．不难理解为什么人们把会话看成一种语用现象，因为会话是语言使用的原型方式，也是我们每个人最初接触语言的形式——语言习得的发源地．最基本、最普通的会话是两个或两个以上的人之间的相互沟通．会话是基本的，因为语言使用的摇篮是孩子与父母间会话的话轮相互交替；会话又是普遍的，它是人类社会共融的规范形式．话轮替换系统是会话最显著的特征之一．Sacks，Schegloff和Jefferson提出了话轮替换系统的最简单的规则．这一规则确定一次只有一个人说话．会话中常出现沉默、中断、失误及重叠现象．话轮替换规则确定了话轮在韵律上和句法上的完成与否，它给语言结构提出了更高的要求． Stephen C. In his book Pragmatics, Levinson defines a conversation as: “a way of talking freely between two or more people, generally excluding such special occasions as religious rituals, Courts, classrooms and similar environments. ” Conversation is a form of communication between speakers for a given purpose in a common environment. It is not hard to understand why conversations are seen as a pragmatic phenomenon because conversations are the prototype of language usage and are the first form of language that each of us is exposed to - the birthplace of language acquisition. The most basic, most common conversation is the communication between two or more people. Conversation is basic, because the cradle of language use is the alternation of words and turns between children and their parents. Conversations are common and form the normative form of communion of human society. The turnaround system is one of the most prominent features of conversations. Sacks, Schegloff and Jefferson proposed the simplest rules for a turn-based replacement system. This rule determines that only one person speaks at a time. Silence, interruptions, mistakes and overlaps often occur in conversations. The turn-based substitution rules determine whether the turn-round is prosodic or syntactic or not, which sets higher demands on the language structure.