The aim of this paper is to illustrate the various uses of the Korean nominal seym `calculation`, ranging from propositional to expressive meanings. An attempt is made at delineating a grammaticalization path, which reveals the extent to which grammaticalization intersects with a number of cognitive mechanisms, such as metaphor, pragmatic inferencing, subjectification, and generalization. In present-day Korean, seym shows diverse functional usages such as a nominal marker, a connective marker, and a sentence final marker. In particular, this item advances in grammaticalization into versatile markers of grammatical concepts, e.g. tense-aspect-modality, style indication, etc. through diverse channels. Considering such versatility of the form as a result of the historical pragmatics and cognitive reanalysis, this paper focuses on the analysis of the semantic and functional changes of seym undergone over time, and discusses what are the possible triggers to cause this versatility to varying degrees within a grammaticalization framework.