To observe the effectiveness of three parts of teacher talk, I will try to identify them from three main aspects according to Cortney B. Cazden (2001:2-6). This thesis will seek to answer the following three research questions: First what are the linguistic characteristics of teacher talk?  Second, which factors lead to teacher’s effective and ineffective talk. 

1.3 Research significance 

English teacher talk is necessary for students not only to impart English knowledge but also for facilitating acquisition process and eliciting learner output. It is the main source of input for most students and target language data. As an important part of English teaching, teacher talk not only provides target language input, instructional directions and organizes class activities as well. Teacher talk provides learners with opportunities to hear and use the target language. If teachers issue instructions and feedback by target language appropriate and comprehensible, students can have higher efficient and involve themselves into learning section actively. However, if teachers instruct with invalid words which are beyond students understanding, like complex words, students will get confused in the process of completing the sections.

2．Literature review

Scholars from both China and America have conducted many studies on classroom discourse analysis, including the study of teacher talk. 

2.1 CLIL and features of classroom discourse

In accordance with Christian Dalton Puff, the term Content and Language Integrated Learning (CLIL) refers to educational settings where a language other than the students’ mother tongue is used as medium of instruction (2007:3). By applying English as medium, it is a clever and economical way to turn CLIL classrooms into “streets”, as it were. Meanwhile, the range of CLIL is from kindergarten to university class.

By using English as medium for non-native speaker, trying to grab the key of the situation, get a control on the discourse, partial topic knowledge and operating in an incompletely known language code has been a big barrier for these students to overcome.

Generally, classroom discourse is pided into two parts: question and feedback. In CLIL class, teachers control the classroom discourse by asking most of the questions as one of the main ways. From Steve Walsh, the feature of classroom discourse obtains “elicitation techniques, repair, modify speech to learners, control communication pattern” (2002:7)