The word Doubtfulnes is misspelled against Doubtfulness, a noun meaning "State of being doubtful."
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Doubtfulness 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:  doubtfulne-s 
Correct Spelling:  doubtfulne-ss 
Check more misspelled words of Doubtfulness to spell it correct.