Genuine, real, or trustworthy; being what it claims to be and not a fake or imitation.
From Medieval Latin 'authenticus' and Greek 'authentikos' (original, genuine), derived from 'authentes' (one who does things himself, a master). The '-al' suffix added to create an adjectival form.
While we mostly use 'authentic' today, 'authentical' persists in some academic and legal writing, and the underlying Greek root meant literally 'done by one's own hand'—connecting authenticity to personal authorship.
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