The First Czechoslovak Republic, often colloquially referred to as the First Republic, was the first Czechoslovak state that existed from 1918 to 1938, a union of ethnic Czechs and Slovaks. The country was commonly called Czechoslovakia, a compound of Czech and Slovak; which gradually became the most widely used name for its successor states. It was composed of former territories of Austria-Hungary, inheriting different systems of administration from the formerly Austrian and Hungarian territories.

Czech, historically also known as Bohemian, is a West Slavic language of the Czech–Slovak group, written in Latin script. Spoken by over 10 million people, it serves as the official language of the Czech Republic. Czech is closely related to Slovak, to the point of high mutual intelligibility, as well as to Polish to a lesser degree. Czech is a fusional language with a rich system of morphology and relatively flexible word order. Its vocabulary has been extensively influenced by Latin and German.