Includes bibliographical references (125-126) and index.
1. Introduction: dimensions of linguistic diversity; 2. How many languages are there in the world?; 3. Phylogenetic linguistics: establishing linguistic relationships; 4. The future of languages; 5. Some problems in the counting of languages; 6. The genotypes of languages; 7. The diversity of signed languages; 8. Conclusion: the unity of human language; References; Further reading.