Russian word сон comes from Proto-Indo-European *seup-, Proto-Indo-European - nós, Proto-Indo-European *sup-n-o-, and later Proto-Indo-European *supnós (Death. Sleep.)
| Dictionary entry | Language | Definition |
|---|---|---|
| *seup- | Proto-Indo-European (ine) | |
| - nós | Proto-Indo-European (ine) | |
| *sup-n-o- | Proto-Indo-European (ine) | |
| *swopnos | Proto-Indo-European (ine) | dream |
| *swópniyom | Proto-Indo-European (ine) | |
| *supnós | Proto-Indo-European (ine) | Death. Sleep. |
| *su(o)pnum | Proto-Balto-Slavic (ine-bsl-pro) | |
| *supnas | Proto-Balto-Slavic (ine-bsl-pro) | Sleep. |
| *sъpnъ | Proto-Slavic (sla-pro) | |
| *sъnъ | Proto-Slavic (sla-pro) | Sleep, dream. |
| сон | Russian (ru) | Dream (imaginary events seen in the mind while sleeping). Sleep. |