Devi and Vrkis feminines
In Vedic Sanskrit, the devÄ« and vį¹kÄ«s inflections are two types of inflection of feminine Ä«-stems exhibiting distinct apophony patterns.
Vį¹kÄ«s
The distinguishing feature of the vį¹kÄ«s inflection is that the Ä« always has the Vedic accent except in the vocative case, and the nominative singular has the desinence -s like non-feminine words. Indeed, while vį¹kÄ«s-words are overwhelmingly of the feminine gender, there are a few members of the class that belong to the masculine gender or are gender indeterminate: rathÄ«- "wain-driver, charioteer" (often applied to Agni, who trafficks sacrificial offerings and divine boons between mortals and immortals).
The inflectional type is usually accepted to reach back into Proto-Indo-European times, with an exact correspondence of Sanskrit vį¹kÄ«s and Old Norse ylgr, both meaning "she-wolf", first described by Karl Verner in 1877 (see Verner's law). The distinction between devÄ« and vį¹kÄ«s dies out in during the Vedic period and PÄį¹ini is unaware of it, classifying Ä«-stems by accentuation (vį¹kÄ«s-words are a subset of NÄ«S).
One formation that has been diachronically connected with the vį¹kÄ«s inflection is Cvi, which in PÄį¹ini's grammar of Classical Sanskrit refers to a formation where an Ä« is added to a nominal stem and compounded with a verbal root kį¹ "to make", as "to be" or bhÅ« "to become", resulting in a factitive verb where the Ä«-stem is indeclinable and used like a preverb. For example, grÄmÄ«bhÅ« "to get possession of a village", from grÄma "village".
Devī
The devÄ« inflection exhibits an ablaut pattern different from the vį¹kÄ«s inflection. PÄį¹ini does not make the distinction, classifying the Ä«-stems by their accentuation (devÄ« words may be NiiN, NiiP or NiiS).