Second language acquisition theory rests on the premise that a second language can never thoroughly be learned after the brain's synapses for language acquisition have closed. In layperson's terms, this means that a person can become fully bilingual, trilingual, etc., provided that the secondary languages are learned before the child reaches age six or seven. Teenagers and adults can gain some
. degree of fluency in a second language, but will never truly speak it like a native speaker.
