English as a second language; ESL; TESOL ; Illiteracy ; Ausspracheregel (Sprachunterricht) ; Pronunciation rule (language teaching) ; GPK (Sprachunterricht) ; Grapheme-phoneme conversion rule (language teaching) ; Glottodidaktik; Lehrforschung; Pädagogische Linguistik; Pedagogical linguistics; Language teaching research ; Written/spoken language ; Processability theory; Language comprehension (second language acquisition) ; English