English as a second language; ESL; TESOL ; Bilingual method ; Instruction (medium of) ; Medium of instruction ; Institutional communication ; Shared intentionality; Collective intentionality; Intersubjectivity ; Classroom communication; Instructional communication ; Alternation (biling.) ; Language shift (biling.) ; Sprachwechsel (biling.) ; Second language acquisition (pragm.) ; Zweitspracherwerb (pragm.) ; Interactionist hypothesis (second language acquisition) ; Conversational analysis (second language acquisition) ; English ; Japanese