Normative discourse about probability requires shared meanings for disciplinary vocabulary. Previous research indicates that students' meanings for probability vocabulary often differ from those of mathematicians, creating a need to attend to developing students' use of language. Current standards documents conflict in their recommendations about how this should occur. In the present study, we conducted microgenetic research to examine the vocabulary use of four students before, during, and after lessons from a cycle of design-based research attending to probability vocabulary. In characterizing students' normative and nonnormative uses of language, we draw implications for the design of curriculum, standards, and further research. Specifically, we illustrate the importance of attending to incrementality, multidimensionality, polysemy, interrelatedness, and heterogeneity to foster students' probability vocabulary development.