So as a multifunctional discourse marker in native and learner speech

► The discourse marker so in a diversified learner corpus and a native corpus. ► Learners use so significantly more often than native speakers. ► In the learner corpus Linguistics students use so more than Economics students. ► So functions in the ideational, interpersonal and textual domains. ► Synchronic study of so's functions points at a possible case of polysemy. This article gauges the extent to which so is used as a discourse marker by Belgian native speakers of Dutch who have almost reached the end of formal instruction in English. The interview corpus compiled for this study is further diversified in order to determine the potential influence of distinct learning objectives in foreign language acquisition, with half of the learner participants majoring in English Linguistics, and the other half in Commercial Sciences. Not only is the use of discourse markers in these two sub-corpora juxtaposed from a quantitative and a qualitative perspective, the learner corpus is also set off against a comparable native speaker corpus. The investigation shows that the language learners use so significantly more often than their English peers, and the students of English Linguistics use so slightly more often than those of Commercial Sciences. All ten discourse marker functions of so, which can be situated in three different domains (ideational, interpersonal and textual), are found both in the learner and the native sub-corpora. An initial tentative account of the interrelatedness of these functions points in the direction of polysemy.