One method is "social interactionism." Here, the relationship between adults who have language and children who do not is paramount. Psychologist Jerome Bruner made the theory popular in the West, but it actually originated in Russia by another psychologist, Lev Vygotsky. Social interactionism privileges feedback between child and parent, or another adult. The adult both teaches and corrects the child as they acquire new words.
A vastly different language acquisition theory is "emergentism." Emergentism postulates that language development is largely biological and that nature plays as great a role in language acquisition as does nurture. Without these automatic biological triggers, language development is not possible.