Plural of grueling; plural noun form referring to multiple grueling experiences, tests, or ordeals.
From the adjective 'grueling' (originally from 'gruel') used as a gerund noun plus the plural '-s', allowing 'grueling' to function as a noun describing experiences.
English is wonderfully flexible—'grueling' starts as an adjective, becomes a gerund (noun), and then pluralizes to describe multiple intense ordeals, showing how one word-form can evolve through the sentence!
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