Kooperation und Interaktion Olga Czyzak Maria Hummel Kooperation interaction Fremdsprachenlernen Deutsch als Fremd- und Zweitsprache Ko-Konstruktion Interaktion foreign language learning co-construction cooperation German as a second language The fifth volume of the Zeitschrift für Interaktionsforschung in DaFZ (ZIAF) focuses on the interplay of cooperation and interaction as an essential element of language learning. The studies presented in this volume shed light on cooperative practices in schools, universities and digital contexts— ranging from group work, peer interaction, language testing and team teaching to virtual exchange and AI-supported learning environments. They show how learners and teachers co-construct language, knowledge, and social relationships through joint action, and how multilingual resources, interaction skills, and reflexivity promote learning processes. At the same time, the need for targeted planning, contextual sensitivity, and openness to new technologies in order to faciliate cooperation becomes obvious. Overall, the issue offers empirically based insights and illustrates cooperation as a central principle of successful language learning in German as a foreign and second language. This introduction outlines the framework of the volume and highlights selected findings of the included contributions. Philipps-Universität Marburg Marburg Deutschhausstraße 9, 35037 Marburg 2025 2025-12-15 2025-12-15 Text article urn:nbn:de:hebis:04-0009-2025-354-89576 ger 3101186-X 5 1 (2025) 1 https://journals.uni-marburg.de/ziaf/article/download/8957/8622 10.17192/ziaf.2025.5.1.8957 https://journals.uni-marburg.de/0009/2025/354/8957