Definition: The term "Slavic Lang" describes a linguistic development in Eastern Europe that began with the arrival of Slavic languages around the late 9th century, marking a significant step forward in the development of modern European languages. Definition: Slavic Lang refers to a branch of linguistics that examines how language and culture have evolved in Eastern Europe over the centuries. It focuses on the interaction between the Old and New Worlds, where the Slavic languages developed from Latin-based cultures that later influenced those within the Slavic languages themselves. In essence, it seeks to understand how Eastern European languages were shaped by the various influences they have experienced, including the Old World's influence and the migration of Slavic peoples. This study not only helps us better understand the development of modern languages but also highlights the importance of language in shaping cultural and historical events.