North Slavic languages

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

for a number of proposed groupings or subdivisions of the Slavic languages. However, "North Slavic" is not widely used in this sense. Modern scholars usually divide the Slavic languages into West Slavic, East Slavic, and South Slavic.^[1]
for the West Slavic and East Slavic languages considered as a combined unit, particularly when contrasted to South Slavic languages.
for a number of constructed languages that were created in the 20th and 21st century, and have been derived from existing Slavic languages.

^ Gołąb, Zbigniew (1992). The Origins of the Slavs: A Linguist's View. Columbus, Ohio: Slavica Publishers. pp. 12–13. The present-day Slavic peoples are usually divided into the three following groups: West Slavic, East Slavic, and South Slavic. This division has both linguistic and historico-geographical justification, in the sense that on the one hand the respective Slavic languages show some old features which unite them into the above three groups, and on the other hand the pre- and early historical migrations of the respective Slavic peoples distributed them geographically in just this way.