How Are First, Second, Heritage, and Dominant Languages Defined and Differentiated in Educational and Research Discourse?

Language-related terminologies play a crucial role in shaping research, policy, and instruction in multilingual education, yet these terms are often used interchangeably despite holding distinct conceptual meanings. Inconsistencies in definitions can hinder comparability, policy implementation, and pedagogical responsiveness. This study aimed to clarify and differentiate key language-related terms such as "first language," "native language," "mother tongue," "second language," "foreign language," "heritage language," and "dominant language" based on current scholarly usage. A systematic literature review was conducted using the Scopus database, applying defined inclusion and exclusion criteria to identify open-access, peer-reviewed journal articles published in 2025. A PRISMA flowchart guided the screening of over 100,000 records, resulting in a final sample of 22 conceptually relevant articles. Findings reveal that first language, native language, and mother tongue share roots in early acquisition but differ in sociocultural and policy implications. Second language and foreign language are distinguished primarily by context of exposure, while heritage language describes minority languages acquired informally with varying levels of proficiency and emotional significance. Dominant language reflects institutional and societal power rather than the order of acquisition. The study concludes that clearer distinctions among these terms are essential for advancing research precision and educational equity. It is recommended that future work explore how learners, educators, and policymakers operationalize these terms in practice to better support multilingual identities and language-inclusive learning environments.