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.


The academic discipline of second-language acquisition is a subdiscipline of applied linguistics. It is broad-based and relatively new. As well as the various branches of linguistics, second-language acquisition is also closely related to psychology, cognitive psychology, and education. To separate the academic discipline from the learning process itself, the terms second-language acquisition researchsecond-language studies, and second-language acquisition studies are also used.

SLA research began as an interdisciplinary field, and because of this it is difficult to identify a precise starting date.[2] However, two papers in particular are seen as instrumental to the development of the modern study of SLA: Pit Corder's 1967 essay The Significance of Learners' Errors, and Larry Selinker's 1972 article Interlanguage.[3] The field saw a great deal of development in the following decades.[2]

Since the 1980s, second-language acquisition has been studied from a variety of disciplinary perspectives, and theoretical perspectives. Significant approaches in the field today are: systemic functional linguistics, sociocultural theory, cognitive linguistics, Noam Chomsky's universal grammarskill acquisition theory and connectionism.[3]

The term acquisition was originally used to emphasize the non-conscious nature of the learning process,[4] but in recent years learning and acquisition have become largely synonymous.

Second-language acquisition can incorporate heritage language learning,[5] but it does not usually incorporate bilingualism. Most SLA researchers see bilingualism as being the end result of learning a language, not the process itself, and see the term as referring to native-like fluency. Writers in fields such as education and psychology, however, often use bilingualism loosely to refer to all forms of multilingualism.[6] Second-language acquisition is also not to be contrasted with the acquisition of a foreign language; rather, the learning of second languages and the learning of foreign languages involve the same fundamental processes in different situations.[7]

There has been much debate about exactly how language is learned, and many issues are still unresolved. There are many theories of second-language acquisition, but none are accepted as a complete explanation by all SLA researchers. Due to the interdisciplinary nature of the field of second-language acquisition, this is not expected to happen in the foreseeable future.


Second-language acquisition can be divided up into five stages: preproduction, early production, speech emergence, intermediate fluency, and advanced fluency.[8] The first stage is preproduction, also known as the silent period. Learners at this stage have a receptive vocabulary of up to 500 words, but they do not yet speak their second language.[8]Not all learners go through a silent period. Some learners start speaking straight away, although their output may consist of imitation rather than creative language use. Others may be required to speak from the start as part of a language course. For learners that do go through a silent period, it may last around three to six months.[9]

The second stage of acquisition is early production, during which learners are able to speak in short phrases of one or two words. They can also memorize chunks of language, although they may make mistakes when using them. Learners typically have both an active and receptive vocabulary of around 1000 words. This stage normally lasts for around six months.[8]

The third stage is speech emergence. Learners' vocabularies increase to around 3000 words during this stage, and they can communicate using simple questions and phrases. They may often make grammatical errors. The stage after speech emergence is intermediate fluency. At this stage, learners have a vocabulary of around 6000 words, and can use more complicated sentence structures. They are also able to share their thoughts and opinions. Learners may make frequent errors with more complicated sentence structures. The final stage is advanced fluency, which is typically reached somewhere between five and ten years of learning the language. Learners at this stage can function at a level close to native speakers.[8]

The time taken to reach a high level of proficiency can vary depending on the language learned. In the case of native English speakers, some estimates were provided by the Foreign Service Institute (FSI) of the U.S. Department of State, which compiled approximate learning expectations for a number of languages for their professional staff (native English speakers who generally already know other languages). Of the 63 languages analyzed, the five most difficult languages to reach proficiency in speaking and reading, requiring 88 weeks (2200 class hours), are ArabicCantoneseMandarinJapanese, and Korean. The Foreign Service Institute and the National Virtual Translation Center both note that Japanese is typically more difficult to learn than other languages in this group.[10][11]

Comparisons with first-language acquisition

Adults who learn a second language differ from children learning their first language in at least three ways: children are still developing their brains whereas adults have conscious minds, and adults have at least a first language that orients their thinking and speaking. Although some adult second-language learners reach very high levels of proficiency, pronunciation tends to be non-native. When a second language learner's speech plateaus, it is known as fossilization.

Some errors that second-language learners make in their speech originate in their first language. For example, Spanish speakers learning English may say "Is raining" rather than "It is raining", leaving out the subject of the sentence. French speakers learning English, however, do not usually make the same mistake. This is because pronominal and impersonal sentence subjects can be omitted (or as in this case, are not used in the first place) in Spanish but not in French.[12] This kind of influence of the first language on the second is known as negative language transfer.

Also, when people learn a second language, the way they speak their first language changes in subtle ways. These changes can be with any aspect of language, from pronunciation and syntax to gestures the learner makes and the things they tend to notice.[13] For example, French speakers who spoke English as a second language pronounced the /t/ sound in French differently from monolingual French speakers.[14] This kind of change in pronunciation has been found even at the onset of second-language acquisition; for example, English speakers pronounced the English /p t k/ sounds, as well as English vowels, differently after they began to learn Korean.[15] These effects of the second language on the first led Vivian Cook to propose the idea of multi-competence, which sees the different languages a person speaks not as separate systems, but as related systems in their mind.[16]