Heritage language is a concept within linguistics, sociolinguistics, and psychology referring to a non-dominant language acquired by an individual, typically from family or community members, within a dominant language environment. As a central research area, it investigates the unique linguistic profiles, acquisition pathways, maintenance challenges, and cognitive and social implications associated with these languages. Key characteristics include diverse proficiency levels, often differing significantly from monolingual norms, and a strong link to cultural identity; its study is vital for advancing understanding of bilingualism, language variation, and the dynamics of language contact and shift.