| No. | Item | Definition |
|---|---|---|
| 1. | axis | the central line of rotation |
| 2. | backbone | the main support structure |
| 3. | base | the foundation or bottom |
| 4. | basis | the main reason or support |
| 5. | bedrock | the solid underlying foundation |
| 6. | body | the main mass of something |
| 7. | bottom line | the essential conclusion or point |
| 8. | building block | a basic unit or part |
| 9. | bulk | the main mass or part |
| 10. | center | the middle or main part |
| 11. | centerpiece | the main feature or focus |
| 12. | central idea | the main idea |
| 13. | central part | the part in the middle |
| 14. | central point | the key point in the middle |
| 15. | chief part | the most important part |
| 16. | convergence | a coming together at a center |
| 17. | cornerstone | the essential foundation element |
| 18. | crossroads | a central meeting point |
| 19. | crux | the decisive point |
| 20. | distillate | the purified essential part |
| 21. | DNA | the essential makeup |
| 22. | driver | the main force behind something |
| 23. | driving force | the main motivating force |
| 24. | element | a basic part |
| 25. | engine | the driving central part |
| 26. | essence | the most basic nature |
| 27. | extract | the essential part taken out |
| 28. | focal point | the center of attention |
| 29. | focus | the central point of attention |
| 30. | foundation | the underlying base or support |
| 31. | framework | the basic supporting structure |
| 32. | fulcrum | the point on which things turn |
| 33. | fundament | the base or foundation |
| 34. | fundamental | a basic essential element |
| 35. | fundamentals | the basic essential elements |
| 36. | gist | the main point or idea |
| 37. | ground | the basis for something |
| 38. | grounds | the basis or reason |
| 39. | groundwork | the basic foundation work |
| 40. | heart | the most important part |
| 41. | hinge | the central turning point |
| 42. | hub | the main center of activity |
| 43. | identity | the essential nature of something |
| 44. | impetus | the driving force |
| 45. | infrastructure | the underlying supporting system |
| 46. | ingredient | a component part |
| 47. | inner layer | the inside layer |
| 48. | inner mechanism | the internal working part |
| 49. | inner part | the inside central portion |
| 50. | inner section | the inside section |
| 51. | inner workings | the essential internal parts |
| 52. | interior | the inside part |
| 53. | junction | a meeting central point |
| 54. | kernel | the central, essential part |
| 55. | key | the most important element |
| 56. | keystone | the central supporting element |
| 57. | linchpin | the essential connecting element |
| 58. | main element | the primary component |
| 59. | main idea | the central idea |
| 60. | main part | the most important part |
| 61. | main point | the most important point |
| 62. | main support | the chief supporting part |
| 63. | main theme | the central theme |
| 64. | mainstay | the chief support or basis |
| 65. | meat | the main substance of something |
| 66. | meeting point | a central place of joining |
| 67. | middle | the central area or part |
| 68. | midpoint | the middle point |
| 69. | nature | the essential character |
| 70. | nexus | a central connection point |
| 71. | node | a central point in a network |
| 72. | nucleus | the central part of something |
| 73. | pillar | a main supporting part |
| 74. | pith | the essential part of something |
| 75. | pivot | the central point of change |
| 76. | premise | the basic idea or basis |
| 77. | primary part | the main part |
| 78. | prime mover | the main driving cause |
| 79. | principal part | the most important part |
| 80. | principle | a fundamental rule or belief |
| 81. | quintessence | the purest essence |
| 82. | rationale | the underlying reason |
| 83. | reason | the explanation or basis |
| 84. | root | the fundamental source or cause |
| 85. | skeleton | the supporting structure |
| 86. | soul | the essential spirit |
| 87. | spine | the central supporting structure |
| 88. | spirit | the essential character |
| 89. | structure | the basic arrangement or framework |
| 90. | substance | the essential material or meaning |
| 91. | substrate | the underlying layer or base |
| 92. | substructure | the underlying supporting structure |
| 93. | support | the thing that holds up |
| 94. | tenet | a central principle |
| 95. | theme | the central topic or idea |
| 96. | thesis | the central argument or idea |
| 97. | underlying part | the part beneath the surface |
| 98. | underpinning | the supporting basis |
| 99. | understructure | the supporting structure beneath |
| 100. | unit | a single part of a whole |
