The quality of being strong and able to withstand pressure, difficulty, or damage without breaking.
From Old English 'tōh' (tough), possibly from Germanic roots meaning 'to pull' or 'to stretch.' The suffix '-ness' converts the adjective into an abstract noun.
Toughness in materials science and in human psychology come from the same principle—the ability to withstand stress and bounce back without permanently deforming. That's why we use the same word for tough leather AND tough people!
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