1. ineffable defying expression or description
  2. inevitability the quality of being unavoidable
  3. affability a disposition to be friendly and approachable
  4. inability lack of capacity to do something
  5. ineffably to an inexpressible degree
  6. invariability a quality of uniformity and lack of variation
  7. infeasibility the quality of not being doable
  8. invisibility the quality of not being perceivable by the eye
  9. infallibility the quality of never making an error
  10. infidelity the quality of being unfaithful
  11. inaudibility the quality of not being perceptible by the ear
  12. immovability not capable of being moved or rearranged
  13. unfeasibility the quality of not being doable
  14. instability a lack of balance or state of disequilibrium
  15. unavailability the quality of not being available when needed
  16. incapability the quality of not being capable -- physically or intellectually or legally
  17. insurability the quality of being insurable
  18. incurability incapability of being cured or healed
  19. unavoidability the quality of being impossible to avoid or evade
  20. ignobility the quality of being ignoble