Eficacity or Efficacity: How To spell?
The word Eficacity is misspelled against Efficacity, a noun meaning "Efficacy."
Efficacity has double "ff" is mispronounced as "f"Remember double 'FF' in between the strings E & icacity which should not be misspelled with single 'F'
Wrong Spelling:  E-f-icacity  Correct Spelling:  E-ff-icacity 
Find more wrongly spelled words of Efficacity to spell it well.