The document discusses language acquisition and its stages. It defines language acquisition as the process of learning one's native or second language. Language acquisition generally refers to first language acquisition, which studies how infants acquire their native language, while second language acquisition looks at additional language learning in children and adults. The stages of first language acquisition discussed include the pre-language stage from 3-10 months, the one-word stage from 12-18 months, the two-word stage from 18-20 months, and the multiple-word stage from 2-3 years. The document also examines theories of language acquisition such as behaviorist learning theory and the nativist approach.