Zonal constructed languages are constructed languages made to facilitate communication between speakers of a certain group of closely related languages. They form a subgroup of the international auxiliary languages, but unlike languages like Esperanto and Volapük they are not intended to serve as languages for the whole world, but merely for a limited linguistic or geographic area. There is some overlap with the term "Euroclone", however, the latter usually refers to languages intended for global use but based (almost) exclusively on European material. Another related concept is known as a koiné language, a dialect which naturally emerges as a means of communication among speakers of divergent dialects of a language.
Most zonal constructed languages were created during the period of National revival at the end of the 19th century, some were created later. Nowadays, most older zonal constructed languages are known only to specialists. Modern examples are Interslavic and Folkspraak.
Most numerous within this category by far are Pan-Slavic languages. The oldest known example is Ruski jezik (1665) by the Croatian priest Juraj Križanić, who is often regarded as the first recorded Pan-Slavist. Other notable examples of early Pan-Slavic language projects are Universalis Lingua Slavica by Ján Herkeľ (1826), Uzajemni Pravopis Slavjanski by the Slovene Matija Majar (1865), Neuslawisch by the Czech Ignac Hošek (1907) and Slavina by the Czech Josef Konečný (1912). Until the beginning of the 20th century, all projects were characterized by a heavily naturalistic grammar, based directly or indirectly on Old Church Slavonic. Their authors were motivated by the belief that all Slavic languages were dialects of one single Slavic language rather than separate languages. They deplored the fact that these dialects had diverged beyond mutual comprehensability, and the language they envisioned was intended to reverse this process. Their long-term objective was that it would replace the individual Slavic languages.