Disimilation or Dissimilation: How To spell?
The word Disimilation is misspelled against Dissimilation, a noun meaning "The act of making dissimilar."
Dissimilation has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings di & imilation which should not be misspelled with single 'S'
Wrong Spelling:  di-s-imilation  Correct Spelling:  di-ss-imilation 
Find more incorrect spellings of Dissimilation to spell right way.