This article offers a particular analytic method from systemic functional linguistics, thematic analysis, which reveals the mathematical meaning potentials construed in discourse. Addressing concerns that discourse analysis is too often content-free, thematic analysis provides a way to represent semantic structures of mathematical content, allows for content comparisons to be drawn between classroom episodes, and identifies points of possible student misinterpretation. Analyses of 2 middle school classroom excerpts focusing on area—1 that derives triangle area formulas from the rectangle area formula and another that connects parallelogram and rectangular area— are used to delineate the method. Descriptions of similarities and differences in the classroom discourse highlight how, in each classroom, mathematical terms such as base and height were used in semantically related but distinct ways. These findings raise the question of whether students were aware of and able to navigate such semantic shifts.

International calls have been made for reasoning-and-proving to permeate school mathematics. It is important that efforts to heed this call are grounded in an understanding of the opportunities to reason-and-prove that already exist, especially in secondary-level geometry where reasoning-and-proving opportunities are prevalent but not thoroughly studied. This analysis of six secondary-level geometry textbooks, like studies of other textbooks, characterizes the justifications given in the exposition and the reasoning-and-proving activities expected of students in the exercises. Furthermore, this study considers whether the mathematical statements included in the reasoning-and-proving opportunities are general or particular in nature. Findings include the fact that the majority of expository mathematical statements were general, whereas reasoning-and-proving exercises tended to involve particular mathematical statements. Although reasoning-and-proving opportunities were relatively numerous, it remained rare for the reasoning-and-proving process itself to be an explicit object of reflection. Relationships between these findings and the necessity principle of pedagogy are discussed.