1. Submarine: A type of ship that operates underwater.
  2. Subway: An underground train system.
  3. Substitute: A person or thing that takes the place of another.
  4. Subtract: To take one number away from another.
  5. Subpar: Below the expected standard.
  6. Subtext: The hidden or underlying meaning of something.
  7. Subdue: To bring under control.
  8. Submerge: To go under the surface of water.
  9. Suburb: An area on the edge of a city.
  10. Subtle: Not obvious; very delicate or precise.
  11. Substandard: Below the usual or required standard.
  12. Subcontract: A contract assigned to a third party.
  13. Subdue: To overpower or bring under control.
  14. Subdivide: To divide something into smaller parts.
  15. Subscript: A small number or letter written below the main text.
  16. Subdue: To overcome or bring under control.
  17. Suburban: Relating to a suburb.
  18. Subzero: Below zero degrees on the temperature scale.
  19. Subcommittee: A smaller group within a larger committee.
  20. Subsequent: Following in time or order.
  21. Subversion: An attempt to overthrow or undermine something.
  22. Subjunctive: A verb form used to express wishes or conditions.
  23. Substitution: The act of replacing one thing with another.
  24. Subclimate: A smaller or less significant climate within a larger one.
  25. Subdivide: To divide into smaller parts.
  26. Subtropical: Relating to regions just outside the tropical zone.
  27. Subcontractor: A person or company hired to do part of another company’s contract.
  28. Subsoil: The layer of earth beneath the topsoil.
  29. Subculture: A group within a larger culture with distinct interests or values.
  30. Subtext: An underlying meaning not explicitly stated.
  31. Subsequence: A series that follows another.
  32. Subatomic: Smaller than atoms; relating to particles within atoms.
  33. Subtlety: The quality of being not obvious; delicate details.
  34. Suburbia: The suburbs collectively; suburban life.
  35. Subseries: A smaller series within a larger series.
  36. Submachine: A type of automatic firearm smaller than a machine gun.
  37. Subchannel: A secondary channel within a main channel.
  38. Subtile: Slightly perceptible or barely noticeable.
  39. Subversive: Intended to undermine or challenge authority.
  40. Subharmonic: A frequency that is a fraction of a fundamental frequency.
  41. Subcontinent: A large, distinct part of a continent.
  42. Subclause: A smaller clause within a larger sentence.
  43. Subrange: A smaller or less important range within a larger one.
  44. Suburbanite: A person who lives in a suburb.
  45. Subtense: A line that represents the distance between two points.
  46. Suborder: A rank in biological classification below the order.
  47. Subordinate: Lower in rank or position.
  48. Subchapter: A chapter within a larger book or document.
  49. Subatomic: Smaller than an atom; particles within atoms.
  50. Subtraction: The operation of taking one number away from another.
  51. Subduing: Bringing something under control.
  52. Sublease: Renting out property you’re already renting.
  53. Substandard: Below the usual or expected standard.
  54. Subsequent: Following in time or order.
  55. Subdue: To bring something under control.
  56. Subaqueous: Relating to or living underwater.
  57. Substrate: The base layer on which something rests or grows.
  58. Subdermal: Beneath the skin.
  59. Substantial: Of considerable importance, size, or worth.
  60. Submersible: Capable of being submerged under water.
  61. Subpolar: Relating to regions near the poles.
  62. Subideal: Below the perfect or desired level.
  63. Subprime: Lower in quality or value than what is ideal.
  64. Submerge: To put something completely under water.
  65. Subvocal: Said or done without speaking aloud.
  66. Subaudible: Below the level of normal hearing.
  67. Subhuman: Below the standard of human beings.
  68. Subreaction: A response that is less intense than usual.
  69. Subdeterrent: Less effective at deterring or preventing.
  70. Subnominal: Below the expected level for a particular standard.
  71. Subtle: Delicate or not obvious.
  72. Suborbital: Not reaching the orbit of a planet or moon.
  73. Subregional: Relating to a smaller area within a larger region.
  74. Substantial: Of great importance or value.
  75. Subspace: A smaller or secondary space within a larger one.
  76. Substitute: To replace something with something else.
  77. Subaltern: Of lower rank or position.
  78. Suboperator: A person who works under another operator.
  79. Subefficient: Less than the desired level of efficiency.
  80. Subdiagnostic: Not enough to diagnose a condition.
  81. Subcarinal: Located below the carina in anatomy.
  82. Subsolars: Areas directly below the sun’s path.
  83. Subaerial: Existing or occurring under the sky.
  84. Subnumerary: Less than the usual or expected number.
  85. Submaximal: Less than the maximum level.
  86. Subfrequent: Occurring less frequently.
  87. Subsyllabic: Relating to parts smaller than syllables.
  88. Subcurvature: A curve less than a full curve.
  89. Subimmunization: A state less than complete immunity.
  90. Subconscious: Existing or occurring below the level of awareness.
  91. Subself: A lesser version of the self or personality.
  92. Subrespiratory: Breathing at a level below normal.
  93. Subdistal: Further from the center than a more proximal point.
  94. Subconsonantal: Relating to sounds below the level of consonants.
  95. Subcaloric: Less than the usual caloric amount.
  96. Sublist: A smaller list within a larger list.
  97. Subcapillary: Relating to or less than the size of capillaries.
  98. Subfungal: Below the level of the fungus or fungal structure.
  99. Subrotational: Less than the expected degree of rotation.
  100. Subcritical: Below the level needed for a reaction or process to be critical.