503. The Nominative case of nouns (or pronouns) is used
1. As the subject of a finite verb.
2. In address, for the vocative.
Zeus is king.
ὦ φίλος εἰπέ.
O friend, speak.
Aesch. Prometheus Bound 545
504. A Nominative may stand as appositive to a sentence.
Nηλεῶς ὧδʼ ἐρρύθμισμαι, Ζηνὶ δυσκλεὴς θέᾱ.
Thus pitilessly am I chastised, a sight of evil fame for Zeus.
Aesch. Prometheus Bound 241