The nominative case
The nominative case is a naming case. Its most frequent function is to indicate the subject of a finite verb.
The subject of a verb will match the person and number of the verb form: a singular noun in the nominative case will have a third person singular verb form, and a nominative plural noun acting as the subject will match a third person plural verb. We use the term agreement to refer to this matching of grammatical properties.
Consider these examples:
ἡ μήτηρ ἐτελεύτησε, “His mother died.”
ἡ μήτηρ is nominative, singular, and feminine, “his mother”. ἐτελεύτησε, “she died,” is from τελευτάω, τελευτήσω, ἐτελεύτησα, τετελεύτηκα, τετελεύτημαι, ἐτελευτήθην, “to die.” It is aorist, active and indicative; since it is in the third person singular, it agrees with the subject ἡ μήτηρ.
τὸ παιδίον ἐβόα, “The baby was crying.”
τὸ παιδίον, “the baby” is neuter nominative singular. ἐβόα, “It was crying,” is from βοάω, βοήσω, ἐβόησα, βεβόηκα, βεβόημαι, ἐβοήθην, “to shout, cry,” and is in the imperfect indicative active. Because it is third person singular, it agrees with the subject τὸ παιδίον.
ἐψόφουν αἱ θύραι, “The doors began to creak.”
αἱ θύραι, “the doors,” is feminine nominative plural. (We’ll see the plural forms of the article and noun in the following section of this module.) ψοφέω “to make a noise” is a regular epsilon contract verb, so this form is the imperfect indicative active. Since it is in the third person plural, it agrees with the subject αἱ θύραι. (Note that subjects can follow the verb in Greek: it is still clear from its nominative case form that it functions as the subject of ἐψόφουν.)
There is one important exception to subject-verb agreement: neuter nominative plural nouns acting as the subject normally take a third person singular verb form.
ταῦτα δίκαια ἦν, “These things were right.”
ταῦτα is the neuter nominative plural of a pronoun we’ll learn in this module (“this, these”). You’ve already learned that ἦν is an imperfect indicative active form of “to be.” It is third person singular: since ταῦτα is neuter plural, the singular verb agrees with the plural subject. (δίκαια is an adjective we’ll learn in this module, meaning “just, right.”)