Understanding is one of the four key ideas in the "Australian Curriculum: Mathematics." This case study investigated preservice teachers' understanding of modified words such as 'regular polygon', where the preceding word/s modifies the meaning of the final word. Data were gathered from 23 preservice teachers who voluntarily participated in a series of learning sessions focused on literacy in mathematics. The study highlights potential difficulties that preservice teachers have with some mathematical concepts described by modified words. Reading the paper has the potential to enhance teachers' understanding of some modified words and challenges associated with their use. This knowledge can be productively used in their teaching. [For the first article in this series of two articles "The Quest to Deepen Understanding in Measurement and Geometry: Confusing Word Groups," see EJ1269467.]