The Slovak language, belonging to the western-Slav language group, is closely related to the Czech language. Both languages are mutually comprehensible and Czechs and Slovaks understand each other. For this reason the Czechs in the past usually considered the Slovaks to be part of the Czech nation and Slovak to be just another dialect of the Czechs. In Slovakia, this idea was not commonly accepted but, still, the idea of Czech-Slovak reciprocity was relatively strong in the nineteenth century. As a result the idea of a common Czecho-Slovak state gradually emanated during the First World War.