[o]

[..]
  1. off_t
  2. offsetof
  3. old_stat
  4. old_utsname
  5. oom
  6. open
  7. open_aux
  8. open_mouse
  9. open_namei
  10. operand_selector
  11. options
  12. origin
  13. out_port_type
  14. outb
  15. outb_p
  16. output_byte
  17. outsw
  18. outw
  19. overlap
[..]