A complex sentence consists of a principal sentence and one or more subordinate, or dependent, sentences. The principal sentence, as each subordinate sentence, has its own subject and predicate. The principal sentence of a complex sentence is called the principal clause, the subordinate sentence is called the subordinate clause. The principal clause may precede or follow the subordinate clause.2174
The principal clause may have any form of the simple sentence.
a. Parentheses belonging to the thought of the entire sentence, but standing in no close grammatical relation to it, count as principal clauses. So οἶμαι, δοκῶ, φημί, ὁρᾷς; οἶδα, οἶδ' ὅτι
The subordinate clause is always introduced by a subordinating conjunction, as εἰ
A finite mood in a subordinate clause may be influenced by the tense of the principal clause. If the verb of the principal clause stands in a secondary tense, the verb of the subordinate clause is often optative instead of indicative or subjunctive, as it would have been after a primary tense. Dependence of mood after a secondary tense is never indicated by the subjunctive.2177
Each tense in a subordinate clause denotes stage of action; the time is only relative to that of the leading verb. A subordinate clause may be marked by change of person in verb and pronoun.2178 2179
A subordinate clause may be coördinate in structure.
ἐπεὶ δ' ἠσθένει Δα_ρεῖος καὶ ὑπώπτευε τελευτὴν τοῦ βίου, ἐβούλετό οἱ τὼ παῖδε παρεῖναι
a. So a relative clause, though properly subordinate, may be equivalent to a coördinating clause: εἰ δ' ὑ_μεῖς ἄλλο τι γνώσεσθε, ὃ μὴ γένοιτο, τίν' οἴεσθ' αὐτὴν ψυ_χὴν ἕξειν; but if you decide otherwise, —
A clause dependent upon the principal clause may itself be followed by a clause dependent upon itself (a sub-dependent clause).
οἱ δ' ἔλεγον (principal clause) ὅτι περὶ σπονδῶν ἥκοιεν ἄνδρες (dependent clause) οἵτινες ἱκανοὶ ἔσονται . . . ἀπαγγεῖλαι (sub-dependent clause)
A verb common to two clauses is generally placed in one clause and omitted from the other (so especially in comparative and relative clauses).
ἥπερ (τύχη) ἀεὶ βέλτι_ον (
ὥσπερ νῦν τούτων οὐδὲν γίγνεται περὶ αὐτόν
The subject of the dependent clause is often anticipated and made the object of the verb of the principal clause. This transference, which gives a more prominent place to the subject of the subordinate clause, is called
δέδοικα δ' αὐτὴν μή τι βουλεύσῃ νέον
ᾔδει αὐτὸν ὅτι μέσον ἔχοι τοῦ Περσικοῦ στρατεύματος
ἐπεμέλετο αὐτῶν ὅπως ἀεὶ ἀνδράποδα διατελοῖεν
a. Anticipation is especially common after
b. When a subordinate clause defines a verbal idea consisting of a verb and a substantive, its subject may pass into the principal clause as a genitive depending on the substantive of that clause:
ἦλθε δὲ καὶ τοῖς Ἀθηναίοις εὐθὺς ἡ ἀγγελία_ τῶ πόλεων ὅτι ἀφεστᾶσι
c. The subject of the dependent clause may be put first in its own clause:
ἐπιχειρήσωμεν εἰπεῖν, ἀνδρεία_ τί ποτ' ἐστίν
d. The object of the subordinate clause may be anticipated and made the object of the principal clause. Thus,
εἰρώτα_ ὁ Δα_ρεῖος τὴν τέχνην εἰ ἐπίσταιτο
e. A still freer use is seen in ἐθαύμαζεν αὐτὸν ὁ Λύ_σανδρος ὡς καλὰ τὰ δένδρα εἴη
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].