The purpose of this study is to explore how mathematics educators understand the terms having lexical ambiguity. Five terms with lexical ambiguity, leave, times, high, continuous, and convergent were selected based on literature review and recommendations of college calculus instructors. The participants consisted of four mathematics educators at a large Midwestern university. The qualitative data were collected from open-ended items in the survey. As a result of analysis, I provided participants' sentences with five terms showing their understanding of each term. The data analysis revealed that mathematics educators were not able to separate the meanings of the words such as leave and high when these words are frequently used in daily life, and the meanings in mathematics context are similar with that in daily context. Lexical ambiguity shown by mathematics educators can help mathematics teachers to understand the terms with lexical ambiguity and improve their instructions when those terms should be found in students' conversations.

In the early stage of lesson enactment process, teachers use textbooks and other resources to select tasks and activities. It follows that discrepancies between textbooks and research-recommended pathways for learning may lead to concerns or issues with pacing in the classroom. To explore this idea further, this study examined the alignment between three popular standards-aligned textbooks series and volume learning trajectories. The results indicated that the standards-based textbooks examined may lack attention to important topics in the pacing of volume instruction, and suggest the need to inform both pre-service and in-service teachers about the gap between textbook lessons and volume learning trajectories so that they will be able to reflect students' thinking in volume learning trajectory to their lessons.

This exploratory study focuses on analyzing three mathematics textbooks in Germany, Singapore and South Korea to reveal similarities and differences in their introductions of fraction concepts. Findings reveal that all three countries' textbooks introduce fraction concepts predominantly by using pictorial representations such as area models, but the introductions of multiple fraction constructs vary. The Singaporean and South Korean textbooks predominantly used a part-whole construct to introduce fractional concepts while the German textbook introduced various constructs sequentially in the first pages using several scenarios from different real-life situations. The findings were represented using visual representations, which we called textbook signatures. The textbook signatures provided configurations of the textbook features across the three countries. At the end of paper, we share insights and limitations about the use of textbook signatures in the research on textbook analysis.