τριταῖος (tritaios)

1. on the third day , used with Verbs so as to agree with the subject, τριταῖοι ἐγένοντο ἐν τῇ Ἀττικῇ (Herdotus Historicus); ἐσβεβληκὼς τριταῖος ἐς Μηλιέας having invaded Melis three days before , (Herdotus Historicus); τρ. γενόμενος after being three days dead, (Herdotus Historicus):—; τριταῖος (i.e. πυρετός); a tertian fever , (Plato Philosophus)
2. of events, lasting three days , (Euripides)
3. generally for τρίτος, (Euripides) (ML)