Slavs
Standardised Slavic languages that have official status in at least one country are: Belarusian, Bosnian, Bulgarian, Croatian, Czech, Macedonian, Montenegrin, Polish, Russian, Serbian, Slovak, Slovene, and Ukrainian.
Croats
Scholars have hypothesized the name Croat ("Hrvat") may be Iranian, thus suggesting that the Croatians were possibly a Sarmatian tribe from the Pontic region who were part of a larger movement at the same time that the Slavs were moving toward the Adriatic. The major basis for this connection was the perceived similarity between "Hrvat" and inscriptions from the Tanais dated to the 2nd and 3rd centuries CE, mentioning the name "Khoro(u)athos". Similar arguments have been made for an alleged Gothic-Croat link. Whilst there is indeed possible evidence of population continuity between Gothic and Croatian times in parts of Dalmatia, the idea of a Gothic origin of Croats was more rooted in 20th century Ustaše political aspirations than historical reality.