10.17192/ziaf.2025.5.1.8957 Czyzak, Olga Olga Czyzak Hummel, Maria Maria Hummel Kooperation und Interaktion Introduction to the fifth issue of ZIAF Zeitschrift für Interaktionsforschung in DaFZ : Vol 5 No 1 (2025) Philipps-Universität Marburg 2025 Kooperation interaction Fremdsprachenlernen Deutsch als Fremd- und Zweitsprache Ko-Konstruktion Interaktion foreign language learning co-construction cooperation German as a second language 2025-12-15 2025-12-15 de JournalArticle https://journals.uni-marburg.de/0009/2025/354/8957 urn:nbn:de:hebis:04-0009-2025-354-89576 https://doi.org/10.17192/ziaf.2025.5.1 https://journals.uni-marburg.de/0009/2025/354/8957/8957.png 2750-249X application/pdf 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. 2750-249X Zeitschrift für Interaktionsforschung in DaFZ Vol 5 No 1 (2025)