early bilingualism
bilingualism attained early in life, either through the simultaneous acquisition of two languages at home or through early exposure to a second language before the completion of first-language acquisition at around age 5. This is often contrasted with late bilingualism, which refers to second-language acquisition after age 5 (or, in some definitions, after the onset of puberty). Early bilingualism is more likely to result in a nativelike command of phonology and grammar than is late bilingualism.