"Second-language acquisition (SLA), sometimes called second-language learning — otherwise referred to as L2 (language 2) acquisition, is the process by which people learn a second language."
The process of acquiring an additional language after one's native language has already been acquired, typically through formal instruction or immersion in a language-rich environment.
"The field of second-language acquisition is regarded by some but not everybody as a sub-discipline of applied linguistics..."
"...the idea that the language that learners use is not simply the result of differences between the languages that they already know and the language that they are learning, but a complete language system in its own right, with its own systematic rules."
"This interlanguage gradually develops as learners are exposed to the targeted language."
"However, languages that learners already know can have a significant influence on the process of learning a new one. This influence is known as language transfer."
"The primary factor driving SLA appears to be the language input that learners receive."
"The input hypothesis developed by linguist Stephen Krashen theorizes that comprehensible input alone is necessary for second language acquisition."
"Krashen makes a distinction between language acquisition and language learning (the acquisition–learning distinction), claiming that acquisition is a subconscious process, whereas learning is a conscious one."
"Krashen argues that consciously learned language rules play a limited role in language use, serving as a monitor that could check second language output for form."
"Subsequent work, by other researchers, on the interaction hypothesis and the comprehensible output hypothesis, has suggested that opportunities for output and interaction may also be necessary for learners to reach more advanced levels."
"Research on how exactly learners acquire a new language spans several different areas."
"Cognitive approaches to SLA research deal with the processes in the brain that underpin language acquisition..."
"Sociocultural approaches reject the notion that SLA is a purely psychological phenomenon and attempt to explain it in a social context."
"Some key social factors that influence SLA are the level of immersion, connection to the L2 community, and gender."
"Linguistic approaches consider language separately from other kinds of knowledge and attempt to use findings from the wider study of linguistics to explain SLA."
"There is also a considerable body of research about how SLA can be affected by individual factors such as age and learning strategies."
"A commonly discussed topic regarding age in SLA is the critical period hypothesis, which suggests that individuals lose the ability to fully learn a language after a particular age in childhood."
"Common affective factors that influence acquisition are anxiety, personality, social attitudes, and motivation."
"Individuals may also lose a language through a process called second-language attrition. This is often caused by a lack of use or exposure to a language over time."
"Finally, classroom research deals with the effect that language instruction has on acquisition."