This study compares the effects of two models of vocabulary instruction: (1) the integrated graphic organizer/discussion model; and (2) the definition-only model on the mathematical vocabulary use of fourth grade students. The integrated model combines a modified Concept of Definition (CD) graphic organizer with the Frayer discussion model. The definition-only model required students to write definitions of key terms after an oral review. Knowledge of measurement concepts in two groups of students was assessed through mathematical writing before and after two weeks of instruction. Results showed a larger number of mathematics concepts recorded by the group using the integrated CD-Frayer model. One major implication of this study is that the CD-Frayer model is an effective method for teaching mathematical vocabulary. (Contains 19 references). (DDR)