flatness
noun
[ ˈflatnəs ]
• the quality of having a level surface without raised areas or indentations.
• "the flatness of the external surface"
• lack of emotion or enthusiasm; dullness.
• "neither the editing nor the score do much to help the film's emotional flatness"
• loss of effervescence in a sparkling drink.
• the quality of a musical sound being below normal pitch.
• "the flatness of the vocals"
