The quality or state of being arduous; the degree of difficulty, effort, and strain required for something.
From 'arduous' (difficult, steep) + '-ness' (noun suffix indicating a quality). This abstract noun evolved to describe the measurable level of difficulty in a task or undertaking.
The 'arduousness' of a task determines whether we even try to do it—medieval writers used this word to decide which quests were worth attempting and which were impossible.
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