Relating to or serving the purpose of confirming or providing confirmation; functioning to verify or establish the truth of something.
From 'confirmation' (the act of confirming) plus the suffix '-al' (relating to or having the nature of). The base 'confirm' comes from Latin 'confirmare,' meaning 'to make firm.'
Words ending in '-ational' are somewhat formal and less common than their '-atory' cousins—you'd more likely hear 'confirmatory evidence' than 'confirmational evidence,' showing how English gravitates toward certain suffixes even when multiple options exist.
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