Stephen Hughes wrote:Jonathan Robie wrote:Here's one place that I think κτήτωρ refers to owners of slaves:
Diod. Sic. 34/5.2.31
οἱ δὲ στρατηγοὶ κωλύειν μὲν ἐπεχείρουν τὴν ἀπόνοιαν τῶν οἰκετῶν͵ κολάζειν δὲ οὐ
τολμῶντες διὰ τὴν ἰσχὺν καὶ τὸ βάρος τῶν κυρίων ἠναγκάζοντο περιορᾶν τὴν ἐπαρχίαν
λῃστευομένην. οἱ πλεῖστοι γὰρ τῶν κτητόρων ἱππεῖς ὄντες ἐντελεῖς τῶν Ῥωμαίων͵ καὶ
κριταὶ τοῖς ἀπὸ τῶν ἐπαρχιῶν κατηγορουμένοις στρατηγοῖς γινόμενοι͵ φοβεροὶ ταῖς
ἀρχαῖς ὑπῆρχον.
The governors tried to repress the madness of the slaves, but did not dare to punish them, and because
of the power and strength of the masters they were forced to disregard the plundering of the province.
For since most of the owners were recognised Roman knights, and were judges for charges against
governors from provinces, they caused fear in the governors.
The
Attalus website also has the interpretation "land owners" for κτήτορες, while the relationship between master and slave uses our familiar κύριοι (I have also taken the liberty to underline some things in your quote to make my point clearer

):
When the affairs of Sicily, after the overthrow of Carthage, had remained successful and prosperous for the space of sixty years, at length war with the slaves broke out for the following reasons. The Sicilians, through the enjoyment of a long peace, grew very rich, and bought up an abundance of slaves; who being driven in droves like so many herds of cattle from the different places where they were bred and brought up, were branded with certain marks burnt on their bodies. 2 Those that were young, they used for shepherds, others for such services as they had occasion. But their masters were very strict and severe with them, and took no care to provide either necessary food or clothing for them, so that most of them were forced to rob and steal, to get these necessities: so that all places were full of slaughters and murders, as if an army of thieves and robbers had been dispersed all over the island. 3 The governors of the provinces, to tell the truth, did what they could to suppress them; but they did not dare punish them, because the masters, who possessed the slaves, were rich and powerful. Therefore every governor was forced to connive at the thefts and rapines that were committed in the province. For many of the landowners (κτήτορες) were Roman knights, and because they judged the accusations brought against the governors for their conduct in the provinces, they were a terror to the governors themselves.
That of course is an interpretation.
Bibliotheque Historique has masters here for κτήτωρ:
la plupart de ces maîtres étaient des chevaliers romains
I think it's clear from the context that the same people described as τῶν κυρίων are also described as τῶν κτητόρων. It's possible that this second term is used to describe them as landowners, and it seems likely that slaveowners would also be landowners who might also be knights, but this is pure speculation.
Suppose we were doing either set of synonyms and antonyms related to κτήτωρ for a new version of Louw and Nida or a paper on the concept of ownership in Hellenistic Greek as understood through the word κτήτωρ and other related words. I think we would have to note both interpretations as possible and go looking for other contexts where certain terms occur together. In some cases, more than one interpretation is possible, so you have to leave your options open until there's enough evidence to make a definitive decision. It takes work and time.
I suppose I would also consider the concept of "owner" in other languages and see if I can find examples where the same concept is present in Greek, e.g. how do ancient Greek texts describe the relationship between a dog and its owner, a sword and its owner, etc.
But language is flexible and creative. We don't usually talk about the owner of a pair of glasses, but people write owner's manuals for glasses. In English, it would be dangerous to say that the word 'owner' is not used for a pair of glasses even if we have a hard time finding examples of that in a small corpus. On the other hand, if there were a specific term used to describe owning a pair of glasses, a dictionary would tell us to use that term rather than 'owner'. I'm thinking of German, where 'essen' means eating done by humans and 'fressen' means eating done by animals.
Stephen Hughes wrote:Methods, learning and process are all essential, but when the science is all said and done, interaction with language comes down to art and leaves you in the vulnerability of subjective choices.
This definitely involves interpretation, but interpretation in light of the available evidence, and gathering and interpreting that evidence takes focused time. Informed interpretation is still somewhat subjective, but careful and systematic.
A good lexicon is going to be much better than the intuition of a non-native speaker of a language. Comparing several lexicons is better. To do better than the lexicons for a given word requires quite a bit of careful work.
ἐξίσταντο δὲ πάντες καὶ διηποροῦντο, ἄλλος πρὸς ἄλλον λέγοντες, τί θέλει τοῦτο εἶναι;
http://jonathanrobie.biblicalhumanities.org/