Emisivity or Emissivity: How To spell?
The word Emisivity is misspelled against Emissivity, a noun meaning "Tendency to emission; comparative facility of emission, or rate at which emission takes place, as of heat from the surface of a heated body."
Emissivity has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings emi & ivity which should not be misspelled with single 'S'
Wrong Spelling:  emi-s-ivity  Correct Spelling:  emi-ss-ivity 
Find more wrongly spelled words of Emissivity to spell it well.