Difusivity or Diffusivity: How To spell?
The word Difusivity is misspelled against Diffusivity, a noun meaning "Tendency to become diffused; tendency, as of heat, to become equalized by spreading through a conducting medium."
Diffusivity has double "ff" is mispronounced as "f"Remember double 'FF' in between the strings Di & usivity which should not be misspelled with single 'F'
Wrong Spelling:  Di-f-usivity  Correct Spelling:  Di-ff-usivity 
Check more misspelled words of Diffusivity to spell it correct.