Reconstruction:Proto-Slavic/čьto

• *čь

From *čь +‎ *-to, from Proto-Balto-Slavic *ki, from Proto-Indo-European *kʷid (cf. *kʷis). Cognate with Lithuanian kìtas (“another, next”) and Latvian cits (“other, different”).

*čьto

1. what (interrogative)

• *něčьto
• *ničьto, *ničь

• *kъto

• East Slavic:
  • Old East Slavic: чьто (čĭto)
    • Old Ruthenian: што (što), що (ščo), счо (sčo), что (čto)
      • Belarusian: што (što), чо (čo) (nonstandard, contraction of genitive), шо (šo) (nonstandard)
      • Carpathian Rusyn: што (što)
      • Ukrainian: що (ščo), шо (šo) (most western and some dialects of central Ukraine), што (što) (some dialects of western Ukraine), чо (čo) (nonstandard, contraction of genitive)
    • Russian: что (što), чё (čo) (nonstandard, contraction of genitive), чо (čo) (nonstandard, contraction of genitive), шо (šo) (nonstandard)
  • Old Novgorodian: цьто (cĭto), цето (ceto), цто (cto), чьто (čĭto), что (čto)
• South Slavic:
  • Old Church Slavonic:

    Cyrillic: чьто (čĭto)

    Glagolitic: ⱍⱐⱅⱁ (čĭto)

  • Bulgarian: що (što)
  • Macedonian: што (što)
  • Serbo-Croatian:

    Cyrillic: (Štokavian) што̏, шта̏, (Čakavian) ча̏ (< *čь)

    Latin: (Štokavian) štȍ, štȁ, (Čakavian) čȁ (< *čь)

• West Slavic:
  • Old Czech: (Gsg. *česo > *čьso >) čso
    • Czech: (Gsg. *česo > *čьso >) co
  • Old Polish: (Gsg. *česo > *čьso >) czso, cso
    • Polish: co
    • Silesian: co
  • Slovak: (Gsg. *česo > *čьso >) čo
  • Polabian: (Gsg. *česo > *čьso >) cü
  • Pomeranian:
    • Kashubian: (Gsg. *česo > *čьso >) co
    • Slovincian: (Gsg. *česo > *čьso >) cô
  • Sorbian:
    • Lower Sorbian: (Gsg. *česo > *čьso >) co
    • Upper Sorbian: što

• Vasmer, Max (1964–1973) “что”, in Oleg Trubachyov, transl., Этимологический словарь русского языка [Etymological Dictionary of the Russian Language] (in Russian), Moscow: Progress