This is a course on social norms, the rules that glue societies together. It teaches how to diagnose social norms, and how to distinguish them from other social constructs, like customs or conventions. These distinctions are crucial for effective policy interventions aimed to create new, beneficial norms or eliminate harmful ones. The course teaches how to measure social norms and the expectations that support them, and how to decide whether they cause specific behaviors. The course is a joint Penn-UNICEF project, and it includes many examples of norms that sustain behaviors like child marriage, gender violence and sanitation practices. This is Part 1 of the Social Norms, Social Change series. In these lectures, I introduce all the basic concepts and definitions, such as social expectations and conditional preferences, that help us distinguish between different types of social practices like customs, descriptive norms and social norms. Expectations and preferences can be measured, and these lectures explain how to measure them. Measurement is crucial to understanding the nature of the practice you are facing, as well as whether an intervention was or was not successful, and why. In Part 2, we will put into practice all we have learned in Part 1. New! Please use this link for a 30% discount on the recommended book that accompanies this course! https://global.oup.com/academic/product/9780190622053/?cc=us&lang=en&promocode=AAFLYG6