Flatnes or Flatness: How To spell?
The word Flatnes is misspelled against Flatness, a noun meaning "Depression of tone; the state of being below the true pitch; -- opposed to sharpness or acuteness."
Flatness 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:  flatne-s  Correct Spelling:  flatne-ss 
Explore spell check of Flatness to spell without errors.