authentĭcus

a, um, adj.
I. that comes from the author, authentic, original, genuine (in the jurists and Church fathers; syn.: verus, germanus): testamentum, Dig. 29, 3, 12: tabulae, the same, ib. 10, 2, 4.—Also subst.: authentĭcum, i, n., the original writing, the original, Dig. 22, 4, 2.
Lewis & Short
A Latin Dictionary, 1879
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