Omision or Omission: How To spell?
The word Omision is misspelled against Omission, a noun meaning "That which is omitted or is left undone."
Omission has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings omi & ion which should not be misspelled with single 'S'
Wrong Spelling:  omi-s-ion  Correct Spelling:  omi-ss-ion 
Find more incorrect spellings of Omission to spell right way.