A study used children's definitions to explore the culture of the classroom from the perspective of the child. Definitions for school-related terms were elicited from first graders in two classrooms of a public elementary school in the Chicago metropolitan area. After having been acclimated to the presence of the researchers, the students were asked to supply and define a list of words for a dictionary intended to enable kindergartners to look up any word they needed to know for the first grade. Analysis of the definitions revealed that nondevelopmental factors such as experience of objects, language, and events exerted a strong influence on both grammatical form and semantic content. When the children had similar experiences with a term they produced homogeneous definitions. When they had different experiences, their definitions were divergent in both form and content. These results suggest that differences in definitions can help a teacher to assess student understanding, to find out where there are gaps and misunderstandings, and to determine whether the children are using experience of language, object, event, or task to learn. (JL)