The quality of being helpful, practical, or having a good purpose; the state of being able to do something valuable.
From 'useful' (from Old English 'use' + 'ful' = full of use) + suffix '-ness' (state or quality of). The concept evolved from practical everyday language rather than scholarly terminology.
Usefulness is such a simple concept, but it's been central to how humans evaluate everything from tools to art—the entire Industrial Revolution was about making things more 'useful'!
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