Present but unindexed: the asymmetric fragmentation of Korean language education research, 1980–2025

Purpose – Korean language education has grown rapidly and been reviewed often, but has rarely been mapped bibliometrically. This article maps the field's thematic, intellectual and social structure and tests whether it coheres as a single literature or divides into several. Design/methodology/approach – Using 5,781 internationally indexed works (1980–2025) from OpenAlex, the study combines document clustering, co-citation analysis, bibliographic coupling and text-based network separation (E–I) indices, each assessed against size-preserving permutation nulls and placebo controls. Findings – The central finding is structural and asymmetric. Nine thematic clusters and six co-citation schools describe the field's surface, but beneath one umbrella label an internationally connected applied-linguistics literature and a domestically oriented multicultural- and immigrant-education literature almost never cite one another: cross-literature ties fall well below chance in bibliographic coupling (E–I = −0.84), abstract similarity (E–I = −0.79) and direct citation (p < 0.001). The multicultural literature is present in output and cited domestically (verified in the Korean Citation Index) yet nearly absent from the internationally indexed record through which the visible field coheres. Originality/value – This is the first field-wide, international-index bibliometric map of Korean language education. It makes a hidden, asymmetric fragmentation visible and measurable, and offers a method transferable to any field gathered under one convenient label. Data and code: https://doi.org/10.5281/zenodo.21815676