Recent attention to the word gap has renewed public interest in the striking vocabulary disparities between children in poverty and their higher income peers during the 1st years of life. Children's outcomes—and the nation's well‐being—could be improved by additional research into the mechanisms of vocabulary learning, as well as translational research that produces effective, feasible early‐education practices in homes and schools. In this review, we first explain the nature and extent of the word gap and then briefly describe research on how children learn words during the early years. Next, we summarize limits of available interventions. Finally, we detail pressing questions that demand additional study and suggest research that could provide answers. Ultimately, we call for new research on word‐learning experiences at home and in school that will support reading and academic success for children at risk.