This study investigates English speakers' interlanguage constructions using the Chinese perfective aspect and the sentence‐final modal particle. The speech data produced by two different levels of learners were collected, compared and analyzed. The results show that although the surface forms of the perfective aspect ‐leand sentence‐finalleare identical, they are learned differently, with the perfective aspect ‐leacquired first. Furthermore, at the early stage of acquisition of sentence‐finalle, English‐speaking learners experience acquisition difficulties and transfer their Ll‐based default value to their L2 Chinese. The explanation for the variation in the acquisitionleis due both to syntactic and semantic/functional sources. Structural markedness and functional and pragmatic complexity are important factors in accounting for the variation in acquiringlefor Chines