The Czechoslovak language (Czech: jazyk československý or českoslovenština, Slovak: Československý jazyk) was a political sociolinguistic concept used in Czechoslovakia in 1920–1938[1] for the definition of the state language of the country which proclaimed its independence as the republic of two nations, i.e. ethnic groups, Czechs and Slovaks.

Meanwhile, the Constitution of 1920 and its derivative acts allowed the usage of minority languages provided that they were spoken by not less than 20% of the local population of certain areas.

The Czech-Slav Society (also called the Society for the Czechoslovak Language and Literature) was created in 1829 by students of the Evangelical Lyceum in Bratislava (German: Preßburg or Pressburg), and became an important entity in the Slovak national movement.

In 1836, Ľudovít Štúr, the leader of the Slovak national revival in the 19th century, wrote a letter to the important Czech historian František Palacký.

The concept of 'Czechoslovakism' was used to justify the establishment of Czechoslovakia to the world, because otherwise the statistical majority of the Czechs as compared to Germans would be rather weak.