Second-language acquisition , second-language learning , or L2 acquisition , is the process by which people learn a second language .Second-language acquisition (often abbreviated to SLA ) also refers to the scientific discipline devoted to studying that process. Second language refers to any language learned in addition to a person's first language ;although the concept is named second -language acquisition, it can also incorporate the learning of third, fourth, or subsequent languages. [ 1 ] Second-language acquisition refers to what learners do;it does not refer to practices in language teaching , although teaching can affect acquisition.