σύν

Etymology
Apparently from a, but further connections are. Younger form of Homeric and Old Attic, 🇨🇬. These probably reflect contaminated with the *ḱ of  along with a conflation of their meanings. 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 🇨🇬 and 🇨🇬 dubious, but if indeed a conflation of and, it s a cognate relation regardless.

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

Preposition

 * 1) beside, with

Usage notes

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