English as a second language; ESL; TESOL ; Interimsgrammatik (Spracherwerb) ; Lernervarietät (Spracherwerb) ; Learner variety (language acquisition) ; Interlanguage (language acquisition) ; Transfer (second language acquisition) ; Transfer (Zweitspracherwerb) ; Cross-linguistic influence (second language acquisition) ; Interference (second language acquisition) ; Indefinite article; Definite article; Unbestimmter Artikel; Bestimmter Artikel; Article ; Case (morph.) ; German ; English