A sentence expresses a thought. Syntax (σύνταξις arranging together) shows how the different parts of speech and their different inflectional forms are employed to form sentences.
DEFINITIONS
§§900–905 · 6 sections
Sentences are either complete or incomplete (904).
Every complete sentence must contain two members:
1. The Subject: the person or thing about which something is said.
2. The Predicate: what is said about the subject.
Thus, τὸ θέρος (subj.) ἐτελεύτᾱ (pred.) the summer | came to an end 3.102, ἦλθε (pred.) κῆρυξ (subj.) a herald | came 3. 113.
Complete sentences are simple, compound, or complex. In the simple sentence subject and predicate occur only once. A compound sentence (2162) consists of two or more simple sentences coördinated: τῇ δ᾽ ὑστεραίᾳ ἐπορεύοντο διὰ τοῦ πεδίου, καὶ Τισσαφέρνης εἵπετο
but on the next day they marched through the plain and Tissaphernes kept following them A. 3.4.18. A complex sentence (2173) consists of a main sentence and one or more subordinate sentences: ὁπότε δέοι γέφῡραν διαβαίνειν, ἔσπευδεν ἕκαστος whenever it was necessary to cross a bridge, every one made haste 3. 4. 20.
Incomplete sentences consist of a single member only. Such sentences stand outside the structure of the sentence. The chief classes of incomplete sentences are
a. Interjections, such as ὦ, φεῦ, αἰαῖ, οἴμοι.
b. Asseverations which serve as a predicate to a sentence spoken by another: ναί yes, surely, οὔ no, μάλιστα certainly, καλῶς very well!
c. Headings, titles: Κῡ́ρου Ἀνάβασις the Expedition of Cyrus, Ἀντιγόνη the Antigone, συμμαχίᾱ Ἀθηναίων καὶ Θετταλῶν
the Alliance of the Athenians and Thessalians C.I.A. /lref>b.
d. Vocatives (1283), and nominatives used in exclamation (1288).
e. Exclamations without a verb: δεῦρο hither!
N.—Examples of such incomplete sentences in English are oh, assuredly, no wonder, right about face, away, fire!