Category:Russian н-declension

The so-called н-declension is a remnant of sound changes that took place in Common Slavic due to a requirement that syllables could not have decreasing sonority. While Late Proto-Indo-European and Late Proto-Slavic had nasal diphthongs consisting of a vowel plus a nasal consonant, such syllables later transitioned into nasal vowels through a process of monophthongization, eventually becoming word-final -я in modern Russian. In the oblique cases, because the nasal moved from the coda of the stem to the onset of the following syllable, the -ен- was preserved rather than being reduced to a nasal vowel.