Which term refers to the primary language a person is most proficient in?

The term that refers to the primary language a person is most proficient in is the dominant language. This language is typically the one a person uses most frequently and feels most comfortable communicating in. A person’s dominant language often shapes their cognitive processes and influences their identity and cultural understanding. It can also be significant in educational contexts, as it often plays a role in how individuals access information and interact with their environment.

In contrast, a heritage language refers to a language that is tied to an individual's familial or cultural background but may not necessarily be the language they are most proficient in. A target language is one that an individual is currently learning or striving to become proficient in, usually in the context of language instruction. Meanwhile, a transfer language relates more to the process of applying knowledge or skills from one language to another during learning, rather than referring to proficiency. Understanding these distinctions is important for educators and language learners as they navigate language development.