18Axx General theory of categories and functors

• 18A05 Definitions, generalizations
• 18A10 Graphs, diagram schemes, precategories, neocategories, See also {20Lxx}
• 18A15 Foundations, relations to logic and deductive systems, See also {03-XX}
• 18A20 Epimorphisms, monomorphisms, special classes of morphisms, null morphisms, factorization (bicategories)
• 18A22 Special properties of functors (faithful, full, etc.)
• 18A23 Natural morphisms, dinatural morphisms
• 18A25 Functor categories, comma categories
• 18A30 Limits and colimits (products, sums, directed limits, pushouts, fiber products, equalizers, kernels, ends and coends, etc.)
• 18A32 Factorization of morphisms (via images, coimages, dominions, codominions), substructures, quotient structures, congruences, amalgams
• 18A35 Categories admitting limits (complete categories), functors commuting with limits, continuous functors, completions
• 18A40 Adjoint functors (representable functors, universal constructions, reflective subcategories, reflections, etc.), constructions of adjoints (Kan extensions, etc.)
• 18A99 None of the above but in this section