Herbert Weir Smyth, A Greek Grammar for Colleges

Subject in the Plural, Verb in the Singular

N.—The neuter plural seems to have been originally in part identical in form with the feminine singular in α_, and to have had a collective meaning.

[*] 959. A plural verb may be used when stress is laid on the fact that the neuter plural subject is composed of persons or of several parts: ““τὰ τέλη τῶν Λακεδαιμονίων αὐτὸν ἐξέπεμψαν” the Lacedaemonian magistrates despatched him” T. 4.88, ““φανερὰ ἦσαν καὶ ἵππων καὶ ἀνθρώπων ἴχνη πολλά” many traces both of horses and of men were plain” X. A. 1.7.17.

a. With the above exception Attic regularly uses the singular verb. Homer uses the singular three times as often as the plural, and the plural less frequently with neuter adjectives and pronouns than with substantives. In some cases (B 135) the metre decides the choice.

[*] 960. Following the construction of δοκεῖ ταῦτα, we find ““δόξαν ταῦτα” when it had been thus decided” X. A. 4.1.13, and also δόξαντα ταῦτα X. H. 3.2.19. See 2078 a.

[*] 961. Pindaric Construction. A masculine or feminine plural subject occasionally is used with ἔστι, ἦν, γίγνεται, as: ““ἔστι καὶ ἐν ταῖς ἄλλαις πόλεσιν ἄρχοντές τε καὶ δῆμος” there are in the other cities too rulers and populace” P. R. 462e. The verb usually precedes, and the subject is still undetermined; hence the plural is added as an afterthought. (Cp. Shakesp. “far behind his worth | Comes all the praises.”) In Greek poetry this construction is rarely used with other verbs. On ἔστιν οἵ, see 2513.

a. ἦν was originally plural (464 e. D), and seems to survive in that use.