The quality of being forceful; strength, power, or vigorous effectiveness in action or expression.
From forceful (force + -ful, Old English -full 'full of') + -ness. The -ful suffix means 'full of' or 'characterized by,' while -ness nominalizes the adjective.
Notice how 'forcefulness' is the *opposite* of 'forcedness'—one means genuine power and effectiveness, the other means strained artificiality. These words show how English uses the same root 'force' but spins it toward completely different meanings depending on what suffixes we add.
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