Already in Old Church Slavonic, the nominative forms of this pronoun had mostly fallen out of use, and were supplanted by reflexes of *onъ (“that over there”) and *tъ (“this, that”). It's not certain whether this had already happened within Proto-Slavic but it is likely.
Following a preposition, a prothetic n- is attached to the pronoun in many Slavic languages, including Old Church Slavonic. This probably arose through resegmentation of prepositions that originally ended in -n; through the law of open syllables, it became preferable to consider the final consonant as part of the next syllable, so it was shifted onto the pronoun.
In all of the descendants, the forms of this pronoun have become part of a suppletive paradigm, and are combined with a nominative form from an unrelated root. The following lists the nominative form of the paradigms that have incorporated forms of *jь as their non-nominative case forms.
- East Slavic:
- South Slavic:
- West Slavic: