The extreme heat made the workers suffer beyond words.
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Derived from 李昌龄's 《乐善录·刘贡父》 (Song): the account of a late-life illness so grave that 'the pain cannot be spoken of' — 苦不可言, the near-identical classical precursor.
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Strongly emphatic. Best reserved for genuine suffering — ongoing hardship, chronic illness, harsh conditions. Using it for minor annoyances sounds melodramatic.
