Illnes or Illness: How To spell?
The word Illnes is misspelled against Illness, a noun meaning "Disease; indisposition; malady; disorder of health; sickness; as, a short or a severe illness."
Illness has double 'ss' in the end mispronounced as 's'Remember double 'SS' appears in the end of this word which should not be misspelled with single 'S'
Wrong Spelling:  illne-s  Correct Spelling:  illne-ss 
Explore spell check of Illness to spell without errors.