The term North Slavic languages is used in three main senses:

Proposed subdivisions

Historically, the term "North Slav" has been used in academia since at least the first half of the 19th century. Since then the concept continued to see use in various publications. The following uses of the term "North Slavs" or "North Slavic" are found: In terms of language, the greatest contrasts are evident between South Slavic tongues and the rest of the family. Moreover, there are many exceptions and whole dialects that break the division of East and West Slavic languages. According to this view, it makes more sense to divide the Slavs into two main linguistic groups: the North Slavs and the South Slavs, which can then be further categorised as the Northwest tongues (Czech, Kashubian, Polish, Silesian, Slovak, and Sorbian) and the Northeast ones (Belarusian, Russian, Rusyn, and Ukrainian) – whereas the Southern branch is split into the widely accepted groups of the Southwest languages (Serbo-Croatian and Slovene) and the Southeast tongues (Bulgarian and Macedonian). This model is argued as being more appropriate and linguistically accurate than the triple dissection of east, west and south. Geographer O.T. Ford also writes of the Slavs being "conventionally" divided into three sub-branches (West, East, South), but "in reality" divided only by geographic isolation into two bands that form two dialect continua: North and South – a view mirrored by linguist Tomasz Kamusella. Tracing back to the Greek East and Latin West split in Late Antiquity, there are cultural divisions within the North Slavonic language family with regard to writing systems and religions: the West Slavic languages mostly use versions of the Latin script and have or historically had a Catholic-majority population, while the East Slavic languages are usually written in the Cyrillic script and have or historically had an Orthodox-majority population. A similar east-west split exists for people speaking South Slavic languages in the Balkans, although the Latin script is spreading in countries where Serbo-Croatian is frequently spoken and the majority population is Orthodox, such as Montenegro. The North Slavic and South Slavic-speaking territories are thus both generally geographically divided between Eastern and Western Christianity, and the great majority of all Eastern Orthodox believers in the world are found in the eastern parts of both the North Slavic and South Slavic areas, while a minority are Eastern-rite Catholics.

Constructed languages

"North Slavic" has been used as a name for several 20th- and 21st-century constructed languages forming a fictional North Slavic branch of the Slavic languages. Their main inspiration is the lack of a North Slavic branch vis-à-vis the traditional West, East and South Slavic branches. Usually, they are part of a larger alternative history scheme and may be based on elements from Old Novgorodian or North Russian dialects, historical pidgins like Russenorsk or interference from non-Slavic languages such as the Uralic languages, the Baltic languages or the North Germanic languages. The best-known examples of constructed North Slavic languages are: Also included in the group of fictional North Slavic languages are five interrelated language projects (Seversk, Slavëni, Slavisk, Lydnevi, Mrezian) created around 2001 by Libor Sztemon, although they lack a fictional background and an explanation what exactly qualifies them as North Slavic.