Larry Selinker introduced the concept of interlanguage in 1972, building on Corder's earlier work on language learners' errors. Interlanguage refers to the transitional rule-based linguistic system that language learners develop between their native language and the target language they are learning. It is accepted as a basic principle in the field of second language acquisition. A learner's interlanguage preserves features of their first language and can overgeneralize rules of the target language as they progress toward proficiency but have not yet mastered it.