The article by Linton C. Freeman reviews the intuitive background and existing measures of structural centrality in social networks, evaluating their consistency with intuitions and interpretability. Three distinct intuitive conceptions of centrality are identified: point centrality, graph centrality, and network centrality. For each conception, three measures are developed—absolute and relative measures of point centrality, and one reflecting the degree of centralization of the entire network. The implications of these measures for the experimental study of small groups are examined. The article also discusses the historical development of centrality measures, from Bavelas's introduction of the concept in 1948 to more recent applications in various fields. It highlights the need for a clearer conceptual foundation and more consistent measurement methods, proposing new measures to address these issues. The article concludes by specifying nine centrality measures based on three conceptual foundations, emphasizing the importance of choosing the appropriate measure based on the empirical problem under examination.The article by Linton C. Freeman reviews the intuitive background and existing measures of structural centrality in social networks, evaluating their consistency with intuitions and interpretability. Three distinct intuitive conceptions of centrality are identified: point centrality, graph centrality, and network centrality. For each conception, three measures are developed—absolute and relative measures of point centrality, and one reflecting the degree of centralization of the entire network. The implications of these measures for the experimental study of small groups are examined. The article also discusses the historical development of centrality measures, from Bavelas's introduction of the concept in 1948 to more recent applications in various fields. It highlights the need for a clearer conceptual foundation and more consistent measurement methods, proposing new measures to address these issues. The article concludes by specifying nine centrality measures based on three conceptual foundations, emphasizing the importance of choosing the appropriate measure based on the empirical problem under examination.