The syntactic dimension of academic language has often been studied with respect to students' difficulties with syntactic features in mathematical textbooks and test items, and these studies have contributed to understanding the communicative role of language. In contrast, the epistemic role of students' language use has mainly been explored in lexical and discourse dimensions. This research has shown that higher order cognitive demands require more elaborate language means. The aim of this article is to contribute to theorizing the epistemic role of syntactic language complexity by means of a topic-specific investigation using the mathematical topic of qualitative calculus, i.e., the informal meanings of amount and change. In order to do this, the learning process study presented in this article investigates 18 eleventh graders' conceptual pathways while dealing with challenging tasks on amount and change. The identification of different syntactic complexities in students' utterances provides an overview of the variance of possible phrase structures. Further, it shows that successive conceptual conciseness requires either increasing syntactic complexity or conceptual condensation. So increasing elaborateness in the lexical and syntactic dimensions seem to compensate each other.