Piotr Romanowski holds a PhD and a post-doctoral degree in linguistics. He is Associate Professor at the Faculty of Applied Linguistics, the University of Warsaw, Poland. His academic interests sit at the intersection of multilingual education and sociolinguistics. He is chief editor of Journal of Multilingual Theories and Practices and the book series Language Learning and Multilingualism. He is the founding member of MultiLingNet. In the academic year 2022/23 he was a Research Fellow at University College London. Anna Seretny is an applied linguists and Professor at the Polish Faculty, the Jagiellonian University, Kraków, Poland. She has an extensive record of research and publications on vocabulary learning in Polish as a foreign and heritage language. Her major academic interests are language learning and teaching, heritage language maintenance and education.