A person's second language or L2, is a language that is not the native language of the speaker, but that is used in the locale of that person. In contrast, a foreign language is a language that is learned in an area where that language is not generally spoken. Some languages, often called auxiliary languages, are used primarily as second languages or lingua francas.
More informally, a second language can be said to be any language learned in addition to one's native language, especially in context of second language acquisition, (that is, learning a new foreign language).
A person's first language is not necessarily their dominant language, the one they use most or are most comfortable with. For example, the Canadian census defines first language for its purposes as "the first language learned in childhood and still spoken", recognizing that for some, the earliest language may be lost, a process known as language attrition. This can happen when young children move, with or without their family (because of immigration or international adoption), to a new language environment.
See main article: Theories of second-language acquisition.
See main article: Second-language acquisition. The distinction between acquiring and learning was made by Stephen Krashen (1982) as part of his Monitor Theory. According to Krashen, the acquisition of a language is a natural process; whereas learning a language is a conscious one. In the former, the student needs to partake in natural communicative situations. In the latter, error correction is present, as is the study of grammatical rules isolated from natural language. Not all educators in second language agree to this distinction; however, the study of how a second language is learned/acquired is referred to as second-language acquisition (SLA).
Research in SLA "...focuses on the developing knowledge and use of a language by children and adults who already know at least one other language... [and] a knowledge of second-language acquisition may help educational policy makers set more realistic goals for programmes for both foreign language courses and the learning of the majority language by minority language children and adults." (Spada & Lightbown, p. 115).
SLA has been influenced by both linguistic and psychological theories. One of the dominant linguistic theories hypothesizes that a device or module of sorts in the brain contains innate knowledge. Many psychological theories, on the other hand, hypothesize that cognitive mechanisms, responsible for much of human learning, process language.
Other dominant theories and points of research include 2nd language acquisition studies (which examine if L1 findings can be transferred to L2 learning), verbal behaviour (the view that constructed linguistic stimuli can create a desired speech response), morpheme studies, behaviourism, error analysis, stages and order of acquisition, structuralism (approach that looks at how the basic units of language relate to each other according to their common characteristics), 1st language acquisition studies, contrastive analysis (approach where languages were examined in terms of differences and similarities) and inter-language (which describes L2 learners’ language as a rule-governed, dynamic system) (Mitchell, Myles, 2004). These theories have all had an impact on second-language teaching and pedagogy. There are many different methods of second-language teaching, many of which stem directly from a particular theory. Common methods are the grammar-translation method, the direct method, the audio-lingual method (clearly influenced by audio-lingual research and the behaviourist approach), the Silent Way, Suggestopedia, community language learning, the Total Physical Response method, and the communicative approach (highly influenced by Krashen’s theories) (Doggett, 1994). Some of these approaches are more popular than others, and are viewed to be more effective. Most language teachers do not use one singular style, but will use a mix in their teaching. This provides a more balanced approach to teaching and helps students of a variety of learning styles succeed.
The defining difference between a first language (L1) and a second language (L2) is the age the person learned the language. For example, linguist Eric Lenneberg used second language to mean a language consciously acquired or used by its speaker after puberty. In most cases, people never achieve the same level of fluency and comprehension in their second languages as in their first language. These views are closely associated with the critical period hypothesis.   
In acquiring an L2, Hyltenstam (1992) found that around the age of six or seven seemed to be a cut-off point for bilinguals to achieve native-like proficiency. After that age, L2 learners could get near-native-like-ness but their language would, while consisting of few actual errors, have enough errors to set them apart from the L1 group. The inability of some subjects to achieve native-like proficiency must be seen in relation to the age of onset (AO). “The age of 6 or 8 does seem to be an important period in distinguishing between near-native and native-like ultimate attainment. More specifically, it may be suggested that AO interacts with frequency and intensity of language use” (Hyltenstam, 1992, p. 364).
Later, Hyltenstam & Abrahamsson (2003) modified their age cut-offs to argue that after childhood, in general, it becomes more and more difficult to acquire native-like-ness, but that there is no cut-off point in particular. Furthermore, they discuss a number of cases where a native-like L2 was acquired during adulthood.
As we are learning more and more about the brain, there is a hypothesis that when a child is going through puberty, that is the time that accents start. Before a child goes through puberty, the chemical processes in the brain are more geared towards language and social communication. Whereas after puberty, the ability for learning a language without an accent has been rerouted to function in another area of the brain—most likely in the frontal lobe area promoting cognitive functions, or in the neural system of hormone allocated for reproduction and sexual organ growth.
As far as the relationship between age and eventual attainment in SLA is concerned, Krashen, Long, and Scarcella, say that people who encounter foreign language in early age, begin natural exposure to second languages and obtain better proficiency than those who learn the second language as an adult. However, when it comes to the relationship between age and rate SLA, “Adults proceed through early stages of syntactic and morphological development faster than children (where time and exposure are held constant) ” (Krashen, Long, Scarcella 573). Also, “older children acquire faster than younger children do (again, in early stages of morphological and syntactic development where time and exposure are held constant) ” (573). In other words, adults and older children are fast learners when it comes to the initial stage of foreign language education.
As for the fluency, it is better to do foreign language education at an early age, but being exposed to a foreign language since an early age causes a “weak identification” (Billiet, Maddens and Beerten 241). Such issue leads to a “double sense of national belonging,” that makes one not sure of where he or she belongs to because according to Brian A. Jacob, multicultural education impacts students' “relations, attitudes, and behaviors” (Jacob 364). And as children learn more and more foreign languages, children start to adapt, and get absorbed into the foreign culture that they “undertake to describe themselves in ways that engage with representations others have made” (Pratt 35). Due to such factors, learning foreign languages at an early age may incur one’s perspective of his or her native country.
Acquiring a second language can be a lifelong learning process for many. Despite persistent efforts, most learners of a second language will never become fully native-like in it, although with practice considerable fluency can be achieved. However, children by around the age of 5 have more or less mastered their first language, with the exception of vocabulary and a few grammatical structures.
Error correction does not seem to have a direct influence on learning a second language. Instruction may affect the rate of learning, but the stages remain the same. Adolescents and adults who know the rule are faster than those who do not. In the first language, children do not respond to systematic correction. Furthermore, children who have limited input still acquire the first language.
In the learning of a second language the correction of errors remains a controversial topic with many differing schools of thought. Throughout the last century much advancement has been made in research on the correction of students’ errors. In the 1950s and 60s the viewpoint of the day was that all errors must be corrected at all costs. Little thought went to students’ feelings or self-esteem in regards to this constant correction (Russell, 2009).
In the 1970s Dulay and Burt’s studies showed that learners acquire grammar forms and structures in a pre-determined, inalterable order, and that teaching or correcting styles would not change this (Russell, 2009).
In this same decade Terrell (1977) did studies that showed that there were more factors to be considered in the classroom than the cognitive processing of the students (Russell, 2009). He contested that the affective side of students and their self-esteem were equally important to the teaching process (Russell, 2009).
A few years later in the 1980s, the strict grammar and corrective approach of the 1950s became obsolete. Researchers asserted that correction was often unnecessary and that instead of furthering students’ learning it was hindering them (Russell, 2009). The main concern at this time was relieving student stress and creating a warm environment for them. Stephen Krashen was a big proponent in this hands-off approach to error correction (Russell, 2009).
The 1990s brought back the familiar idea that explicit grammar instruction and error correction was indeed useful for the SLA process. At this time, more research started to be undertaken to determine exactly which kinds of corrections are the most useful for students. In 1998, Lyster concluded that “recasts” (when the teacher repeats a student’s incorrect utterance with the correct version) are not always the most useful because students do not notice the correction (Russell, 2009). His studies in 2002 showed that students learn better when teachers help the student recognize and correct his own error (Russell, 2009). Mackey, Gas and McDonough had similar findings in 2000 and attributed the success of this method to the student’s active participation in the corrective processes (Russell, 2009).
Learners in both languages have knowledge that goes beyond the input they received, in that they are able to construct correct utterances (e.g. phrases, sentences, and questions) that they have never seen or heard before.
Success in language learning can be measured in two ways: likelihood and quality. First language learners will be successful in both measurements. It is inevitable that all people will learn a first language and with few exceptions, they will be fully successful. For second language learners, success is not guaranteed. For one, learners may become fossilized or stuck as it were with ungrammatical items. (Fossilization occurs when language errors become a permanent feature. See Canale & Swain (1980), Johnson (1992), Selinker (1972), and Selinker and Lamendella (1978).) The difference between learners may be significant. Finally, as noted elsewhere, L2 learners rarely achieve complete native-like control of the second language.
|Speed||NA||acquisition is rapid|
|Stages||systematic stages of development||systematic stages of development|
|Error correction||not directly influential||not involved|
|Depth of knowledge||beyond the level of input||beyond the level of input|
|Success (1)||not inevitable (possible fossilization*)||inevitable|
|Success (2)||rarely fully successful||successful|
Being successful in learning a second language can seem like a daunting task. Research has been done to look into why some students are more successful than others. Stern (1975), Rubin (1975) and Reiss (1985) are just a few of the researchers who have dedicated time to this subject. They have worked to determine what qualities make a "good language learner" (Mollica, Neussel, 1997). Some of their common findings are that a good language learner uses positive learning strategies, is an active learner who is constantly searching for meaning. Also a good language learner demonstrates a willingness to practice and use the language in real communication. He also monitors himself and his learning, has a strong drive to communicate, and has a good ear and good listening skills (Mollica, Neussel, 1997).
In pedagogy and sociolinguistics, a distinction is made between second language and foreign language, the latter being learned for use in an area where that language is not generally spoken. Arguably, English in countries such as India, Pakistan, Bangladesh, the Philippines, the Scandinavian countries and the Netherlands can be considered a second language for many of its speakers, because they learn it young and use it regularly; indeed in southern Asia it is the official language of the courts, government and business.
The same can be said for French in Algeria, Morocco and Tunisia, although—as with English in the Scandinavian countries and the Netherlands—French is nominally not an official language in any of these Arabic-speaking countries. In practice, French is widely used in a variety of contexts in these countries, and public signs are normally printed in both Arabic and French. A similar phenomenon exists in post-Soviet states such as Ukraine, Uzbekistan, Kyrgyzstan and Kazakhstan, where Russian can be considered a second language, and there are large Russophone communities there.
In China (with the exception perhaps of Hong Kong), however, English must be considered a foreign language due to the lack of a number of characteristics, such as historical links, media, opportunities for use, and similar vocabulary. Likewise, French would be considered a foreign language in Romania and Moldova. This is despite Romanian and French being Romance languages (unlike Chinese and English, which come from two different language families). This is also despite Romania and Moldova being the only two countries in the world where Romanian is an official language at the national level, Romania's historical links to France, and both Romanian-speaking countries' membership in the Francophonie.
George H. J. Weber, a Swiss businessman and independent scholar, founder of the Andaman Association and creator of the encyclopedic andaman.org Web site, made a report in December 1997 about the number of secondary speakers of the world's leading languages.  Weber used the Fischer Weltalmanach of 1986 as his only source for the L2-speakers data, in preparing the data in the following table. These numbers should be compared with those referred to by Ethnologue, a popular source in the linguistics field.
|Language||data-sort-type="number"||L2 speakers (Weltalmanach 1986)||data-sort-type="number"||L2 speakers (Ethnologue.com)|
|1. French||190 million||50 million|
|2. English||150 million||data-sort-value="500 million"||>430 million|
|3. Russian||125 million||110 million|
|4. Portuguese||28 million||15 million|
|5. Arabic||21 million||246 million|
|6. Mandarin||20 million||178 million|
|7. Spanish||20 million||60 million|
|8. German||9 million||28 million|
|9. Japanese||8 million||1 million|