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Fausset's Bible Dictionary [1]

Called "Javan"  Genesis 10:2. The Ionia on the W. of Asia Minor, whence perhaps emigrants originally passed to Attica and the Peloponnese. The Ionians of secular history however were a colony from Attica. Being the most eastern of the Greeks they were the first known to the Asiatics. Joel ( Joel 3:6) mentions the Grecians as the purchasers to whom the Tyrian slave merchants sold the children of Judah (800 B.C.). Ezekiel ( Ezekiel 27:13) mentions Javan (Greece) and Tyre as "trading in the persons of men." Daniel ( Daniel 8:5;  Daniel 8:21;  Daniel 11:3) foretold the rise of Alexander the Great, "the great horn between the eyes of the rough goat" which "came from the W. on the face of the whole earth, and touched not the ground (overrunning the earth with incredible swiftness, the 'leopard'  Daniel 7:6), and smote the ram" (Medo-Persia).

Zechariah ( Zechariah 9:13) represents Judah and Ephraim as the arrows filling God's bow, "when I have raised up thy son, O Zion, against thy sons, O Greece" (Javan) thus foretelling that the Jewish Maccabees would punish Greece in the person of Antiochus Epiphanes, one of Alexander's successors, in just retribution for her purchasing from Tyre as slaves" the children of Judah and Jerusalem." Isaiah ( Isaiah 66:19) foretells that the Jews who survive His judgments He will send as missionaries to Javan to "declare My glory among the Gentiles." The most important function Greece performed in the gospel scheme was that it furnished the language adapted by its wide use among the refined of all nations, as also by its marvelous flexibility, capability of forming new theological terms, and power of expressing the most delicate shades of meaning, for conveying to the world the glad news of salvation through Christ.

Orally, it was generally used by the apostles in preaching, being then widely spoken; and it is the sole medium of the New Testament written word. The Greek of the New Testament and of the Grecians or Hellenist Jews was not Classical Greek, but Hebrew modes of thought and idiom clothed with Greek words. The Septuagint and the Hebrew are a necessary key to this New Testament Hellenistic Greek. The Grecians or Greek-speaking Jews were at once Jewish missionaries to the pagan, witnessing everywhere against the prevalent polytheism, and pioneers to prepare unconsciously the way for the gospel missionary. They formed the connecting link between the Hebrew Jews and the Gentiles. In  Acts 20:2 "Greece" (Hellas) means Greece Proper, or "Achaia," i.e. southern Greece including the Peloponnese, as opposed to Macedonia on the N. In New Testament "Greek" (Helleen is distinguished from "Grecian" (Hellenist)).

"Greek" means either a native of Greece or else a Gentile in general ( Romans 10:12;  Romans 2:9-10, margin) "Grecian" is a foreign Jew, literally, one who speaks Greek, as contrasted with a home Jew, a "Hebrew," dwelling in Palestine, or rather one speaking the sacred tongue, Hebrew, whether dwelling in Palestine or elsewhere. So Paul though of the Greek city Tarsus, calls himself a "Hebrew" and "of the Hebrew," i.e. having neither parent Gentile ( Philippians 3:5;  2 Corinthians 11:22). The first church at Jerusalem was composed of these two classes, the "Hebrew" and the "Grecian" Jews; from whence, when the Grecian widows complained of being "neglected in the daily ministrations" of alms, the seven chosen to rectify matters were all "Grecians," judging from their Greek names, Stephen, Prochorus, etc.

"Greeks" in the strict sense, whether native Greeks or Gentiles in general, were not admitted to the Christian church until later.  Acts 11:20, "Greeks" is the reading of the Alexandrinus manuscript rightly for "Grecians," for the "Grecians",were long before a recognized portion of the church ( Acts 6:1), and some of those "scattered abroad" were among them (for none of the seven" Grecian" deacons, except Stephen, was as yet martyred) (See Christian ); the new name marking the new epoch in the church. At first those scattered abroad "preached to, the Jews only" (the word is not "Hebrew" but "Jews," including "Grecians"); afterward some of them preached to pagan "Greeks." Their conversation was a new thing, a special "grace of God," tidings of which reaching the Jerusalem church constrained them to send Barnabas as far as Antioch, who "when he had seen the Grace of God was glad" and enlisted the cooperation of Paul who had been in vision already called to "bear Christ's name unto the Gentiles" ( Acts 9:15).

"Spake ALSO unto" is the true reading ( Acts 11:20, the Alexandrinus, the Vaticanus, the Sinaiticus manuscripts, and the Vulgate version). The "also" marks a further step than their "preaching unto the Jews (including 'Grecians') only." It was with the Grecians (Hellenists) that Paul came into controversy at his first visit to Jerusalem ( Acts 9:29). Their Grecian or foreign culture and education made them clever disputants; hence, their keenness in controverting the new convert who had before sided with them against Stephen; the latter also was once a Grecian (Hellenist) Jew before his conversion to Christianity ( Acts 7:58;  Acts 6:9-14).

People's Dictionary of the Bible [2]

Greeks, Grecians . The "Greeks" were those Greeks by race,  Acts 16:1;  Acts 16:3;  Acts 18:17 A. V., but the R. V. omits "the Greeks" and reads "they all;" or else Gentiles as opposed to Jews,  Romans 2:9-10, "Gentile" A. V., but the margin of the A. V. and the text of the R. V. read "Greek." But Grecians were foreign Jews as distinct from those in Palestine, who were called "Hebrews."  Acts 11:20. The Greeks and Hebrews first met when the Tyrians sold the Jews to the Greeks.  Joel 3:6. "Prophetical notice of Greece occurs in  Daniel 8:21, etc., where the history of Alexander and his successors is rapidly sketched.  Zechariah 9:13 foretells the triumphs of the Maccabees over the Græco-Syrian empire, while Isaiah looks forward to the conversion of the Greeks, amongst other Gentiles, through the instrumentality of Jewish missionaries.  Isaiah 66:19."

Morrish Bible Dictionary [3]

1. Sons of Javanim, Greeks. The children of Israel had been sold to them by Tyre and Sidon.   Joel 3:6 .

2. Ἑλληνιστής, Hellenists. Greek-speaking Jews, not to be confounded with Gentile Greeks. They stand in contrast to the Hebrews in   Acts 6:1 . Paul disputed with them at Jerusalem.  Acts 9:29 . The gospel was preached to them at Antioch,  Acts 11:20; but in this last passage many MSS read 'Greeks.'

Easton's Bible Dictionary [4]

 Acts 6:1 9:29 Joel 3:6