What term is used to describe a common language that evolves and influences various dialects in a region?

The term that describes a common language that evolves and influences various dialects in a region is "koine." A koine arises when speakers of different dialects or languages come into contact and develop a mutual, simplified version of their languages that serves as a common means of communication. This term is particularly relevant in historical contexts, such as the Hellenistic period when Greek served as a lingua franca across diverse regions. As speakers adapt this common language, it may influence and give rise to regional dialects, making it a pivotal concept in linguistic studies.

Pidgin, on the other hand, refers to a simplified form of speech that develops for communication between speakers of different native languages, often in trade contexts, and does not necessarily evolve into a standard form. Cree is an indigenous language spoken in Canada and does not pertain to the concept of a common language influencing multiple dialects. Slang consists of informal words or phrases typically belonging to a particular group or culture, rather than a unified language that impacts dialects.