The preface to the second edition of "Categories for the Working Mathematician" introduces the book's structure and content. The book is divided into several chapters, each focusing on different aspects of category theory. Key topics include: 1. **Categories, Functors, and Natural Transformations**: Discusses the axioms for categories and foundational concepts. 2. **Constructions on Categories**: Explores duality and other constructions. 3. **Universals and Limits**: Introduces universal arrows and limits. 4. **Adjunctions**: Provides an in-depth look at adjunctions. 5. **Limits**: Explains the creation of limits. 6. **Monads and Algebras**: Covers monads in categories and their algebras. 7. **Monoids**: Focuses on monoidal categories and monoids. 8. **Abelian Categories**: Discusses kernels, cokernels, additive categories, and diagram lemmas. 9. **Special Limits**: Introduces filtered limits. 10. **Kan Extensions**: Explains adjunctions and limits. 11. **Symmetry and Braiding in Monoidal Categories**: Discusses symmetric monoidal categories. The book also includes a section on structures in categories, such as internal categories, and an appendix covering the foundations. Additional resources include tables of standard categories, terminology, and a bibliography.The preface to the second edition of "Categories for the Working Mathematician" introduces the book's structure and content. The book is divided into several chapters, each focusing on different aspects of category theory. Key topics include: 1. **Categories, Functors, and Natural Transformations**: Discusses the axioms for categories and foundational concepts. 2. **Constructions on Categories**: Explores duality and other constructions. 3. **Universals and Limits**: Introduces universal arrows and limits. 4. **Adjunctions**: Provides an in-depth look at adjunctions. 5. **Limits**: Explains the creation of limits. 6. **Monads and Algebras**: Covers monads in categories and their algebras. 7. **Monoids**: Focuses on monoidal categories and monoids. 8. **Abelian Categories**: Discusses kernels, cokernels, additive categories, and diagram lemmas. 9. **Special Limits**: Introduces filtered limits. 10. **Kan Extensions**: Explains adjunctions and limits. 11. **Symmetry and Braiding in Monoidal Categories**: Discusses symmetric monoidal categories. The book also includes a section on structures in categories, such as internal categories, and an appendix covering the foundations. Additional resources include tables of standard categories, terminology, and a bibliography.