From Proto-Indo-European *h₁en (“in”). Often assumed to come from the zero-grade, cf. Lithuanian į; there are, however, no secure examples of *n̥ > Balto-Slavic *un (other examples like *sъto are all riddled with difficulties and unreliable), and the o-grade *h₁on can be posited instead.
- (+ locative) in, inside, within (stationary)
- (+ accusative) in, into, inside (motion to)
- (+ accusative) at (a moment in time)
- (+ locative) in, during (a period of time)
Because of the law of open syllables, the final -n was normally dropped. But when combined with a stem that (originally?) began with a vowel, it was attached to the following word.
- East Slavic:
- South Slavic:
- West Slavic:
- Vasmer (Fasmer), Max (Maks) (1964–1973), “в”, in Etimologičeskij slovarʹ russkovo jazyka [Etymological Dictionary of the Russian Language] (in Russian), translated from German and supplemented by Trubačóv Oleg, Moscow: Progress
- Derksen, Rick (2008), “*vъ(n)”, in Etymological Dictionary of the Slavic Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 4), Leiden, Boston: Brill, →ISBN, page 530