The volume discusses the current state of international comparative Third Sector research and potential avenues for future development of the field. Building on seminal work by Helmut Anheier and Lester Salamon, the volume provides necessary updates to ensure further Third Sector research is relevant and impactful due to the changing landscape of international relations and the way that the Third Sector interacts with the state, corporates, and wider civil society to face the new global challenges: environmental, economic and social.

The book is articulated in five sections that are organized to move from "theory" to "definition" and "classification" towards "aggregation" (measurement, counting), plus one section dedicated to the relationship between Third Sector and faith. The sixth and final section synthesizes the scientific conversation developed in the five previous ones and opens new research paths for the future.

Encompassing multi-disciplinary approaches and international points of view, the volume is directed towards graduate students and researchers across the academic spectrum as well as practitioners and policymakers working in the Third Sector.

This is an open access book.