Orthographia bohemica

De orthographia bohemica (English: On Bohemian Orthography) is a Latin work published between 1406 and 1412. It is attributed to Charles University rector and reformer Jan Hus. The book codified the Czech language's modern spelling and orthography and had decisive impact on the orthography of a number of other European languages.

Orthographia bohemica was the first known document in which spelling reforms were suggested for a Slavic language. It introduced, among other reforms, the diacritic signs ´ and ˇ which are now besides Czech used in the Baltic languages Lithuanian and Latvian, in other Slavic languages like Croatian, Slovak, Slovenian and partly Polish, and in several other European languages.