How do we know whether a node is important in a network? How can we compare the structure of different networks? These are key questions in network analysis and this week we will start to think about how we describe networks. One of the most popular concepts in network analysis is centrality. That is, important nodes are those who are central. Also, we can compare networks by examining how they differ (or are similar) based on the distribution of centrality scores. This section introduces the concept of centrality, focusing specifically on three different operationalizatons: degree, closeness, and betweenness.