Scholars interested in the function of language in mathematical learning often draw on Vygotsky, whose early work on word meaning has shaped many research studies. However, near the end of a rather short life, Vygotsky heavily critiqued his own previous work and began to sketch a radical theory revision, which overturns much of what he had done and is famous for. The purpose of the present study is to elaborate a possible avenue of such a theoretical revision. This study develops the new theory in the course of an exemplary analysis. The data derive from a scientific laboratory, where three scientists discuss a graph as it evolves in real time before their eyes and as a result of transformations designed to recover the real signal from the noise that is apparently present. Implications of the emerging theory for mathematics education are discussed.