This article presents the results of a design-based research study related to slope that took place in a high school algebra 1 classroom. In the study, students explored situations related to making predictions. As students engaged with these situations, they reinvented and made meaningful multiple subconstructs of slope. I present the findings in the form of a learning trajectory for slope, which describes how learning happened over time, the principles that guide the design of activities that support this learning, and the rationale for how the activities support learning.