This qualitative study examined how three teachers of upper elementary students used science vocabulary in their lessons. The data revealed that teachers used vocabulary to label science phenomena and interpret scientific concepts for students. The practice of labeling was used more extensively than interpreting. Teachers did not help their students understand why scientists use language in these two ways or how one informs the other. Implications for science educators include using inquiry to explicitly teach the purposes of scientific language in order to enhance elementary teachers' knowledge of how vocabulary can aid student understanding of science. (Contains 3 tables.)