Eastern Slavic:
* Belarus: Belarusian
* Russia: Russian
* Ukraine: Ukrainian
West Slavic:
* Czech Republic: Czech
* Poland: Polish
* Slovakia: Slovak
South Slavic:
* Bosnia and Herzegovina: Bosnian, Serbian, Croatian
* Bulgaria: Bulgarian
* Croatia: Croatian
* Macedonia: Macedonian
* Montenegro: Montenegrin
* Serbia: Serbian
* Slovenia: Slovene
Other:
* Kazakhstan: Russian is an official language alongside Kazakh.
* Latvia: Russian is spoken by a significant minority.
* Lithuania: Russian is spoken by a significant minority.
* Moldova: Russian is spoken by a significant minority.
* Romania: Romanian is a Romance language, but it has borrowed words from Slavic languages.
* Transnistria: Russian and Moldovan are official languages.
* Other countries: Slavic languages are also spoken by significant minorities in other countries, such as Germany, Hungary, and Romania.
Important Notes:
* Some Slavic languages are closely related and mutually intelligible to a certain degree (e.g., Czech and Slovak).
* In countries like Bosnia and Herzegovina, Serbia, and Croatia, the same language (Serbo-Croatian) exists with varying dialects and standards.
* The linguistic landscape is complex, and the exact number of speakers of each Slavic language varies depending on the criteria used.
This list provides a general overview, but the specific situation in each country is more complex and dynamic.