Lehrbuch; Arbeitsbuch; Course book; Textbook; Workbook; Übungsbuch; Introductions (to linguistics) ; Second language acquisition (language teaching) ; Zweitspracherwerb (Unterricht) ; Foreign language teaching ; Metalinguistic awareness; Phonologische Bewusstheit; Phonological awareness; Focus on form (language teaching) ; Sprachbewusstsein; Linguistic awareness ; Spracherwerb und neurologische Entwicklung; Language acquisition and neurological development; Sprache und Denken (Ontogenese) ; Language and thought (ontogenesis) ; Cognitive development; Language acquisition and cognitive development ; Zweitspracherwerb (ungesteuerter) ; Second language acquisition (untutored) ; Natürlicher Zweitspracherwerb; Second language acquisition