Expertnes or Expertness: How To spell?
The word Expertnes is misspelled against Expertness, a noun meaning "Skill derived from practice; readiness; as, expertness in seamanship, or in reasoning."
Expertness 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:  expertne-s  Correct Spelling:  expertne-ss 
Explore spell check of Expertness to spell without errors.