<![CDATA[The patterns of Indonesian language acquisition and use among multilingual learners constitute a complex process, as they involve both previously acquired linguistic knowledge and the cognitive processes underlying language comprehension and production. This study aims to describe the patterns of Indonesian language acquisition and use among multilingual learners within a learning context, adopting a psycholinguistic perspective. A qualitative approach was employed. The research subjects consisted of 20 multilingual learners at the State University of Surabaya, ranging from basic to intermediate proficiency levels. The data comprised learner utterances reflecting the processes of acquiring and using Indonesian during instructional interactions. Data collection methods included observation, participant observation, interviews, audio recording, note-taking, task assignments, and documentation. Data analysis involved data reduction, data presentation, and conclusion drawing, while data validity was verified through triangulation and expert review. The results indicate that patterns of Indonesian acquisition and use are manifested through processes such as lexical searching, repetition, self-correction, the use of filler words, and the utilization of previously mastered linguistic knowledge. Basic-level learners tended to exhibit more frequent planning and searching for linguistic forms, whereas intermediate-level learners demonstrated more fluent speech production and a more diverse vocabulary. These differences suggest that the acquisition and use of Indonesian are linked to proficiency levels, multilingual experience, and processes of language planning and processing. The findings confirm that Indonesian language acquisition among multilingual learners unfolds dynamically through the interaction of prior linguistic knowledge, lexical access, and language production processes.]]>
