pentăgōnĭus

a, um, adj.
I. quinquangular, pentagonal.— Subst.: pentăgōnĭum, i, n., a pentagon (post-class.): pentagonii ratio, Auct. de Limit. p. 257 Goes.—pentăgōnum, i, n., for pentaphyllon, App. Herb. 2.
Lewis & Short
A Latin Dictionary, 1879
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