169. The subject of a plural verb may be expressed by means of a collective noun.
ὣς φάσαν ἡ πληθύς
thus they said, the multitude
(cp. Il. 15.305, 23.157).
Conversely, a participle construed with a collective noun and singular verb may be plural.
Il. 18.604 περιΐσταθʼ ὅμιλος τερπόμενοι
Cp. Il. 16.281 ἐκίνηθεν δὲ φάλαγγες ἐλπόμενοι, also Od. 11.15.
In these instances, again, the construction is said to be "according to the meaning" (§ 166), The principle is evidently that an abstract or collective word may be used in apposition to a concrete sword. It may be noticed however that the combinations such as ὅμιλος - τερπόμενοι are only found when there is some pause between the words; otherwise the genitive would be used (construed as in Τρώων κατεδύσεθʼ ὅμιλον, etc.).