A language shift occurs when children become as fluent in their new language as they are in their home language.

Language shift refers to the process by which a speech community in a contact situation (usually a bilingual or multilingual situation) gradually stops using one of its two or more languages in favor of the other. The shift can lead to the eventual death of the less-used language. It is not merely about individual bilingual fluency but about a community-wide transition from one language to another.