Evidence for the Development of L2 Grammar‐for‐Interaction: The Case of Wenti shi (“the Problem Is”) in L2 Chinese Interaction

ABSTRACT This study adopts an integrated framework combining Conversation Analysis for Second Language Acquisition (CA‐for‐SLA), Usage‐Based Linguistics (UBL), and Interactional Linguistics (IL) to trace the longitudinal development of an L2 Chinese learner's use of the construction wenti shi (“the problem is”, WTS) over a 15‐month period. Although quantitative analysis shows that the overall frequency of WTS did not increase substantially, qualitative findings reveal a clear developmental trajectory. Initially employed in its literal sense to present a factual problem, WTS was later mobilized to foreground an issue by upgrading the speaker's epistemic stance and projecting further talk. Building on this core function, two trajectories of functional expansion emerged: one oriented to managing topic transition and the other to prefacing contrasting stance and, eventually, disagreement. These functional developments were accompanied by changes in the construction's syntactic formatting, prosodic chunking, and sequential positioning, each unfolding at a different pace. By tracing the developmental trajectory of WTS, the study demonstrates how grammar‐for‐interaction emerges through the interplay between semantic persistence and interactional needs, while also showing that discourse‐marker‐like development can emerge even in constructions with relatively low token frequency.