Neil Thin sets out to clarify the meaning of the social dimensions of development, with an emphasis on sustainability. He outlines a conceptual framework to facilitate better communication and understanding as a basis for improved policies, implementation strategies and learning strategies. Thin reviews the concepts of social development as currently used in policy documents, operational work, theoretical texts, and monitoring and evaluation. He relates the meaning of social development to core concepts of sustainable development, and to other specific concepts such as the economy and the environment as well as more closely related categories such as social sectors, social welfare and social security. His conclusion is that social development would be more useful as a category of policy and practice if it were relinked with the concept of society and with positive efforts to build or facilitate social progress. Neil Thin draws on his recent research and advisory work on social development policy, poverty reduction strategies, human rights assessment, and evaluation and learning strategies for the analysis and examples.