English as a second language; ESL; TESOL ; Idioms (language teaching) ; Textbook analysis ; Disclaimers; Mitigation (pragm.) ; Abschwächung (pragm.) ; Verschleierung; Downtoner; Diminisher ; Contradicting; Widersprechen; Rebuttal; Gainsaying; Widerstand; Resistance; Disagreement ; Negotiation (communication situation) ; English as international medium ; Second language acquisition (pragm.) ; Zweitspracherwerb (pragm.) ; Interactionist hypothesis (second language acquisition) ; Conversational analysis (second language acquisition) ; English