Fortisimo or Fortissimo: How To spell?
The word Fortisimo is misspelled against Fortissimo, an adverb meaning "Very loud; with the utmost strength or loudness."
Fortissimo has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings forti & imo which should not be misspelled with single 'S'
Wrong Spelling:  forti-s-imo  Correct Spelling:  forti-ss-imo 
Find more incorrect spellings of Fortissimo to spell right way.