Language is an exquisitely efficient means of passing on to children the knowledge that accumulates in a culture. In this research, we focus on information communicated through one type of linguistic structure—the generic sentence—and test whether this information shapes children's developing theories and reasoning about natural kinds (Part I) and social groups (Part II). In Part I, we argue and present evidence for the hypothesis that novel facts conveyed in generic sentences (e.g., “Snakes have holes in their teeth”) are construed as more important, more conceptually central than the same facts conveyed in non-generic sentences (e.g., “This snake has holes in his teeth”). In Part II, we extend this argument to social categories and show that the generic/non-generic distinction influences how preschool-age children and adults interpret new information about social others. We also demonstrate that the influence of generic language is modulated by the nature of the social categories and the properties involved. Our results illustrate the power of linguistically-conveyed information to influence children's theories about the natural and social realms.