How do people adapt to organizational culture and what are the consequences for their outcomes in the organization? These fundamental questions about culture have previously been examined using self-report measures, which are subject to reporting bias, rely on coarse cultural categories defined by researchers, and provide only static snapshots of cultural fit. In contrast, we develop an interactional language use model that overcomes these limitations and opens new avenues for theoretical development about the dynamics of organizational culture. To illustrate the power of this approach, we trace the enculturation trajectories of employees in a mid-sized technology firm based on analyses of 10.24 million internal emails. Our language-based measure of changing cultural fit: (1) predicts individual attainment; (2) reveals distinct patterns of adaptation for employees who exit voluntarily, exit involuntarily, and remain employed; and (3) demonstrates that rapid early cultural adaptation reduces the risk of involuntary, but not voluntary, exit.