су-

Inherited from Proto-Slavic *sǫ-. Cognate with Old Church Slavonic сѫ- (sǫ-). From either Proto-Indo-European *sm̥- (“one, same”) or Proto-Indo-European *ḱom (“with”). Further cognate with Old Prussian san-, sen, Lithuanian sán-, są́-, Latvian suo- (the latter three being nominal prefixes), along with Old Lithuanian sa-, sù-, Sanskrit सम् (sam), स (sa), Avestan 𐬵𐬀𐬨- (ham-), 𐬵𐬀- (ha-), Ancient Greek ὁμοῦ (homoû, “together with”), ἅμα (háma, “together with”), ἁ- (ha-, “with”), Latin semel (“once”).

Etymologically identical to the verbal prefix с- (s-), from Proto-Slavic *sъ(n)-. The difference in development is because of the looser juncture between early Proto-Slavic verbs and preverbs: thus, preverbal *sun was subject to Slavic Auslautgesetze. A similar situation is found in modern German. Not to be confused with Proto-Slavic *sъ- (“good”), from Proto-Indo-European *h₁su-.

A similar or equivalent prefix appears in a few words in Old Church Slavonic as соу- (sou-), with no trace of a nasal vowel, e.g. соугоубь (sugubĭ, “double”), with the root of -гиба́ть (-gibátʹ, “to bend”); compare Russian сугу́бый (sugúbyj, “strict, pure, (originally) double”). Some linguists believe this to be a distinct suffix, while Vasmer sees (in this case at least) assimilation from earlier *sǫ-, as above.

• IPA^(key): [sʊ]

су́- or су- • (sú- or su-)

1. com-, con- (forms nouns denoting a connection or link)

   су- (su-) + nominal form (with o-vocalism, Proto-Slavic -ǫ-) corresponding to -прячь (-prjačʹ, “to yoke, to join”) (root пряг- (prjag-)) → супру́г (suprúg, “husband”)

   су- (su-) + nominal form of сесть (sestʹ, “to sit”) (root сед- (sed-), Old East Slavic сѣд- (sěd-)) → Old East Slavic сусѣдъ (susědŭ, “neighbor”) → Russian сосе́д (soséd, “neighbor”) (with change of prefix vowel, influenced by со- (so-))

   су- (su-) + порос- (poros-, “pig”) (compare порося́ (porosjá), поросёнок (porosjónok)) + -ость (-ostʹ) → супоро́сость (suporósostʹ, “pregnancy (in a pig)”)

2. (forms nouns denoting incompleteness)

   су- (su-) + мрак (mrak, “darkness”) → су́мрак (súmrak, “dusk”)

   су- (su-) + доро́га (doróga, “road, passage”) + -ица (-ica) → судоро́жица (sudoróžica, “impassability (during the rainy season), mudslide”)

   су- (su-) + nominal form (with o-vocalism) corresponding to дёргать (djórgatʹ, “to pull, to throb”) → су́дорога (súdoroga, “cramp”) (dialectal су́дорга (súdorga))

• Not a productive prefix.