ἑνδεκαιδέκατος

From LSJ

ἀλλ᾽ ἀμφὶ τοῖς σφαλεῖσι μὴ 'ξ ἑκουσίας ὀργὴ πέπειρα → to those who err in judgment, not in will, anger is gentle | men's wrath is softened toward those who have erred unwittingly

Source

Spanish (DGE)

-η, -ον
el undécimo día crítico en las enfermedades, Gal.15.822.