In linguistics, mutual intelligibility is a relationship between languages or dialects in which speakers of different but related varieties can readily understand each other without prior familiarity or special effort. It is sometimes used as an important criterion for distinguishing languages from dialects, although sociolinguistic factors are often also used.
Statue of the first Czechoslovak president Tomáš Garrigue Masaryk (whose mother was Czech and father Slovak) with Czech flag on the left and Slovak flag on the right. There is a high level of mutual intelligibility between the closely related West Slavic languages Czech and Slovak (the Czech–Slovak languages).