ksun / Indo-European roots
Preposition and preverb meaning "with"
1. syn- from Greek sun, xun, together, with.
2. Basic form *su(n)-.
a. soviet from Old Russian compound sŭvětŭ, assembly;
b. sputnik from Russian so-, s-, with, together. a and b from Old Russian sŭ(n)-, with, together.
[In Pokorny 2. sem- 902.]