This paper examines the change in young children's understanding of "equal", "more", "less", and "between", words commonly used in equivalent and non-equivalent situations, over a 3-year period. Seventy-six children participated in the longitudinal study. Each year they were asked to share their understanding of these four words. Past research has indicated that many children have limited understanding of "equal" as quantitative sameness. The results of this research suggested that many children also have limited understanding of "more" and "less" and that these understandings did not significantly change over the 3-year period.