Universal Decimal Classification

  1. Habits of plants. Plant behaviour. Plant ecology. Plant ethology. The plant and its environment. Bionomics of plants
  2. Halides
  3. Handbooks. Manuals
  4. Handwritten documents (autograph, holograph copies). Manuscripts. Pictorial documents (drawings, paintings)
  5. Hard surfacing of highways. Pavement, carpet or wearing course. Preparation and use of materials
  6. Harmony. Counterpoint. Melody
  7. Haulage and handling. Hoisting. Winding. Surface transport
  8. Hausa
  9. Headgear. Hatmaking. Millinery
  10. Health and hygiene in relation to age, sex, ethnicity
  11. Health and hygiene of leisure, recreation, sleep
  12. Health and hygiene of the nervous system. Health and ethics
  13. Heat and cold application
  14. Heat conduction. Heat transfer
  15. Heat economy. Fuel economy. Fuels. Heating
  16. Heat engines (except steam engines)
  17. Heat engines in general. Generation, distribution and use of steam. Steam engines. Boilers
  18. Heat or fuel economy in general. Combustion. Natural fuels
  19. Heat treatment operations and equipment
  20. Heat. Thermodynamics. Statistical physics
  21. Heating, ventilation and air conditioning of buildings
  22. Hebrew
  23. Heraldry
  24. Herbaceous or non-woody plants (often called 'plants' or 'flowers')
  25. High ball games with large ball
  26. High explosives
  27. High level, top level of administration. Central, national government
  28. Higher education. Universities. Academic study
  29. Higher mental processes
  30. Highway engineering
  31. Highways in general. Roads. Carriageways. Streets. Rural and urban road systems
  32. Hinayana Buddhism. The lesser vehicle. Theravada Buddhism. Pali school
  33. Hindi
  34. Hindi language
  35. Hindi literature
  36. Hinduism narrowly
  37. Historical geology. Stratigraphy
  38. Historical sources
  39. History
  40. History as a science
  41. History as literary genre. Historical writing. Historiography. Chronicles. Annals. Memoirs. Journals. Diaries. Biography. Autobiography
  42. History of civilization. Cultural history
  43. History of economic theories, doctrines, dogmas
  44. History of the faith, religion, denomination or church
  45. Home affairs. Internal policy
  46. Home economics. Domestic science. Housekeeping
  47. Home economics. Housekeeping, furnishing and equipping a home etc. for particular kinds of person
  48. Hominidae
  49. Honduras. Republic of Honduras. República de Honduras
  50. Hong Kong. Xianggang (Hsiang-Kang)
  51. Horology. Determination and standardization of time
  52. Horse racing. Mounted racing
  53. Horticulture in general. Specific crops
  54. Household appliances and machines. Labour-saving devices in the home
  55. Human ancestry groups
  56. Human beings, born or unborn, living or dead
  57. Human biology
  58. Human geography (cultural geography). Geography of cultural factors
  59. Human relations in the enterprise. Personnel management
  60. Human-computer interaction. Man-machine interface. User interface. User environment
  61. Hungarian
  62. Hungarian language
  63. Hungarian literature
  64. Hungary. Hungarian Republic. Magyarorszag. Magyar Köztársaság
  65. Hunting
  66. Hunting. Fishing. Fish breeding
  67. Hydraulic energy. Water power. Hydraulic machinery
  68. Hydraulic engineering and construction. Water (aquatic) structures
  69. Hydraulic engineering in general
  70. Hydrosphere. Water in general. Hydrology
  71. Hydrostatics in general
  72. Hygiene generally. Personal health and hygiene
  73. Hygiene of air, water, soil. Pollution and its control
  74. Hygiene of dwellings
  75. Hylobatidae
  76. Hypermedia. Hypertext
  77. Hyperspace (space of more than three dimensions)
  78. Hyracoidea. Procaviidae