English as a second language; ESL; TESOL ; Discourse analysis (pragm.) ; Diskursgrammatik; Gesprächsanalyse; Konversationsgrammatik; Conversational analysis (pragm.) ; Classroom communication; Instructional communication ; Speaker strategy ; Second language acquisition (pragm.) ; Zweitspracherwerb (pragm.) ; Interactionist hypothesis (second language acquisition) ; Conversational analysis (second language acquisition) ; English