Plonness or Plainness: How To spell?
The word Plonness is misspelled against Plainness, a noun meaning "The quality or state of being plain."
Word contains consecutive vowels 'AI' in between alphabets pl & nness is misspelled as 'O'Wrong Spelling:  pl-o-nness  Correct Spelling:  pl-ai-nness 
Find more incorrect spellings of Plainness to spell right way.