©2023 Joakim E. Hansen, Erik Eliassen, Anna Sara H. Romøren, Rasmus Kleppe, Nina Gram Garmann & Elisabeth Bjørnestad. This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License (https:// creativecommons.org/licenses/BY/4.0/). Citation: Hansen, J. E., Eliassen, E., Romøren, A. S. H., Kleppe, R., Garmann, N. G. & Bjørnestad, E. (2023). Acquisition of the majority language in Norwegian ECEC: Relating language-learning environment in ECEC to expressive vocabulary. Nordisk barnehageforskning, 20(1), 56–76. https://doi.org/10.23865/nbf.v20.293 Peer-reviewed article | Vol. 20, No. 1, 2023, pp. 56–76 | ISSN: 1890-9167 Acquisition of the majority language in Norwegian ECEC: Relating language-learning environment in ECEC to expressive vocabulary Joakim E. Hansen University of Stavanger, Norway Contact corresponding author: Joakim E. Hansen, e-mail: joakim.e.hansen@uis.no Erik Eliassen Norwegian Institute of Public Health (NIPH) Anna Sara H. Romøren Oslo Metropolitan University, Norway Rasmus Kleppe Queen Maud University College of Early Childhood Education, Norway Nina Gram Garmann Oslo Metropolitan University, Norway Elisabeth Bjørnestad Oslo Metropolitan University, Norway Abstract Developing profciency in the language(s) spoken in any given society is crucial for the inclusion and attainment of children in that society. With an enrolment rate in Norwegian early childhood education and care (ECEC) of 93.4% for children between age one and fve, ECEC constitutes an important out-of- home learning environment for children in Norway. In this study, we examine how the quality of language- learning environments in toddler and preschool groups predicts children’s expressive vocabulary in the majority language depending on children’s home languages. Data from the quality rating scales ITERS-R