σύν

• ξύν (xún) — Homeric, Old Attic
• σούν (soún) — Boeotian

Apparently from a Proto-Hellenic *ksún, but further connections are uncertain. Younger form of Homeric and Old Attic ξύν (xún), Mycenaean Greek 𐀓𐀱 (ku-su /⁠*ksun⁠/). These probably reflect Proto-Indo-European *som- (“one, together (with)”) contaminated with the *ḱ of *ḱóm (“beside, with”) along with a conflation of their meanings ^[1] However, the /u/ is unexpected and unexplained under this proposal. Note that a derivation from *som- alone is impossible, since the *s- would be expected to give h- (aspiration); neither is the ks- explainable from *ḱóm alone. This makes its exact relation to Lithuanian sù and Proto-Slavic *sъ(n) dubious, but if indeed a conflation of *ḱóm and *som-, then it's a cognate relation regardless.

The dative that this preposition governs continues the PIE comitative-instrumental.

σῠ́ν • (sún) (governs the dative)

1. beside, with

• In compounds it has similar applications, including completeness, simultaneity.

• μεταξύ (metaxú)
• ξυνός (xunós)
• συν- (sun-)

• Greek: συν (syn)
• Yevanic: שִׁין (šin)
• → Dutch: syn-
• → English: syn-, sym-
• → French: syn-
• → German: syn-
• → Italian: sin-, sim-
• → Polish: syn-

• “σύν”, in Liddell & Scott (1940) A Greek–English Lexicon, Oxford: Clarendon Press
• σύν in Bailly, Anatole (1935) Le Grand Bailly: Dictionnaire grec-français, Paris: Hachette
• σύν in Cunliffe, Richard J. (1924) A Lexicon of the Homeric Dialect: Expanded Edition, Norman: University of Oklahoma Press, published 1963
• G4862 in Strong, James (1979) Strong’s Exhaustive Concordance to the BibleWoodhouse, S. C. (1910) English–Greek Dictionary: A Vocabulary of the Attic Language‎^[1], London: Routledge & Kegan Paul Limited.
  • conjunction idem, page 160.
  • with idem, page 983.
• Sihler, Andrew L. (1995) New Comparative Grammar of Greek and Latin, Oxford, New York: Oxford University Press, →ISBN