§ 17
In certain expressions, the article is put elliptically with an adjective or similar defining adjunct, a particular substantive being understood, from which the article takes its gender. (Usually in the feminine, because the masculine article suggests only the general notion of a person; the neuter, that of a thing.) Ἡ ἡμετέρα (γῆ), ἐν τῇ τῶν πολεμίων, ἐν τῇ βασιλέως (Pl. Alcib. i. 421). Ἡ αὔριον (ἡμέρα). Κατὰ τὴν ἐμήν (γνώμην). Τὴν ἐπὶ Βαβυλῶνος ἰέναι (ὁδόν). Τὴν ἐπὶ θανάτῳ ἄγειν τινά (to lead one to execution), and similar expressions denoting the direction of a motion. (Of the Adjectives see the further § 87 b.)
§ 18 (51)
(Appendix to Chap. 2.[^1])
a) The Greeks are more regular than we in their use of the plural of substantives, in speaking of a number of individuals and of things which each of these individuals possesses (e.g. ψυχαί, σώματα).
Rem. Sometimes however the singular is used, so that the notion is given in a merely general way: Τὸν πηλὸν ἐπὶ τοῦ νώτου ἔφερον (Thuc. 4, 4). Τὰς πρώρας καὶ τῆς νεὼς ἄνω ἐπὶ πολὺ (a good bit) κατεβύρσωσαν (Thuc. 7, 65); especially without the article, distributively: Δώδεκα ψιλοὶ ξὺν ξιφιδίῳ καὶ θώρακι (Thuc. 8, 22).[^14]
b) Even substantives denoting abstract and other general conceptions to which the notion of number does not apply, are put in the plural to mark the occurrence of the condition, affection, or the like, in different forms, with different subjects or at different times, or with some special modification, e.g. ψύχη καὶ θάλπη, αὔχμοι, πλοῦτοι, δυναστεῖαι, ἔνδειαι, ταπεινότητες, γέλωτες (γέλωτες ἐξαίσιοι), μέσαι νύκτες, midnight, κρέα (conceived as pieces), πυροί, κριθαί (wheat, barley, as masses), ἅλες.
c) Conversely, certain words, denoting individual objects which admit of being numbered, sometimes stand in the singular, to denote the genus and a multitude, e.g. πλίνθος, bricks, or tiles. Note especially the figurative use of ἀσπίς, to signify a host of heavy-armed (poetically, λόγχη), and of ἵππος (ἡ) for the cavalry, with the numerals χιλία and μυρία in the singular: Herodotus has even ἡ κάμηλος, denoting a troop of camels.
[^1] Strictly speaking this does not come under the Syntax.