Whenever two people meet, negotiations take place. If they want to express solidarity and sympathy, they tend to seek common features in their behavior. If speakers wish to express distance towards or even dislike of the person they are speaking to, the reverse is true, and differences are sought. This mechanism also extends to language, as described in the Communication Accommodation Theory.

Some multilinguals use code-switching, a term that describes the process of 'swapping' between languages. In many cases, code-switching is motivated by the wish to express loyalty to more than one cultural group,[citation needed] as holds for many immigrant communities in the New World. Code-switching may also function as a strategy where proficiency is lacking. Such strategies are common if the vocabulary of one of the languages is not very elaborated for certain fields, or if the speakers have not developed proficiency in certain lexical domains, as in the case of immigrant languages.

This code-switching appears in many forms. If a speaker has a positive attitude towards both languages and towards code-switching, many switches can be found, even within the same sentence.  If, however, the speaker is reluctant to use code-switching, as in the case of a lack of proficiency, he might knowingly or unknowingly try to camouflage his attempt by converting elements of one language into elements of the other language through calquing. This results in speakers using words like courrier noir (literally mail that is black) in French, instead of the proper word for blackmail, chantage.

Sometimes a pidgin language may develop. A pidgin language is a fusion of two languages that is mutually understandable for both speakers. Some pidgin languages develop into real languages (such as papiamento in Curaçao orSinglish in Singapore) while others remain as slangs or jargons (such as Helsinki slang, which is more or less mutually intelligible both in Finnish and Swedish).[clarification needed] In other cases, prolonged influence of languages on each other may have the effect of changing one or both to the point where it may be considered that a new language is born. For example, many linguists believe that the Occitan language and the Catalan language were formed because a population speaking a single Occitano-Romance language was divided into political spheres of influence of France and Spain, respectively. Yiddish is a complex blend of Middle High German with Hebrew and borrowings from Slavic languages.

Bilingual interaction can even take place without the speakers switching. In certain areas, it is not uncommon for speakers each to use a different language within the same conversation. This phenomenon is found, amongst other places, in Scandinavia. Most speakers of Swedish, Norwegian and Danish can communicate with each other speaking their respective languages, while few can speak both (people used to these situations often adjust their language, avoiding words that are not found in the other language or that can be misunderstood). Using different languages is usually called non-convergent discourse, a term introduced by the Dutch linguist Reitze Jonkman. To a certain extent, this situation also exists between Dutch and Afrikaans, although everyday contact is fairly rare because of the distance between the two respective communities. The phenomenon is also found in Argentina, whereSpanish and Italian are both widely spoken, even leading to cases where a child with a Spanish and an Italian parent grows up fully bilingual, with both parents speaking only their own language yet knowing the other. Another example is the former state of Czechoslovakia, where two closely related and mutually intelligible languages (Czech and Slovak) were in common use. Most Czechs and Slovaks understand both languages, although they would use only one of them (their respective mother tongue) when speaking. For example, in Czechoslovakia it was common to hear two people talking on television each speaking a different language without any difficulty understanding each other. This bilinguality still exists nowadays, although it has started to deteriorate after Czechoslovakia split up 

Japanese, English, and Russian sign in Northern Japan

Because it is difficult or impossible to master many of the high-level semantic aspects of a language (including but not limited to its idioms and eponyms) without first understanding the culture and history of the region in which that language evolved, as a practical matter an in-depth familiarity with multiple cultures is a prerequisite for high-level multilingualism. This knowledge of cultures individually and comparatively, or indeed the mere fact of one's having that knowledge, often forms an important part of both what one considers one's own personal identity to be and what others consider that identity to be.  Some studies have found that groups of multilingual individuals get higher average scores on tests for certain personality traits such as cultural empathy, openmindedness and social initiative.  The idea of linguistic relativity, which claims that the language people speak influences the way they see the world, can be interpreted to mean that individuals who speak multiple languages have a broader, more diverse view of the world, even when speaking only one language at a time.  Some bilinguals feel that their personality changes depending on which language they are speaking;  thus multilingualism is said to create multiple personalities. Xiao-lei Wang states in her book Growing up with Three Languages: Birth to Eleven: "Languages used by speakers with one or more than one language are used not just to represent a unitary self, but to enact different kinds of selves, and different linguistic contexts create different kinds of self-expression and experiences for the same person." However, there has been little rigorous research done on this topic and it is difficult to define “personality” in this context. François Grosjean wrote: "What is seen as a change in personality is most probably simply a shift in attitudes and behaviors that correspond to a shift in situation or context, independent of language."  However, the Sapir-Whorf hypothesis, which states that a language shapes our vision of the world, may suggest that a language learned by a grown-up may have much less emotional connotations and therefore allow a more serene discussion that a language learned by a child and to that respect more or less bound to a child's perception of the world.

Bilinguals who are highly proficient in two or more languages are reported to have enhanced executive function  and are better at some aspects of language learning compared to monolinguals. Research indicates that a multilingual brain is nimbler, quicker, better able to deal with ambiguities, resolve conflicts, and resist Alzheimer’s disease and other forms of dementia.  There is also a phenomenon known as distractive bilingualism or semilingualism. When acquisition of the first language is interrupted and insufficient or unstructured language input follows from the second language, as sometimes happens with immigrant children, the speaker can end up with two languages both mastered below the monolingual standard.  For example, the East Bengal rooted bangali Muslim community of Assam province in India. As mentioned, their mother tongue is Bangla. But they have no opportunity to study in the MT in the school. Their medium language of study is Assamese, i. e., the provincial language. So they communicate in a mean language standard mixing both the mother tongue and the medium language. Because they have no chance to study both the languages separately, they can't differentiate between the two and maintain it in expression. Literacy plays an important role in the development of language in these immigrant children.  Those who were literate in their first language before arriving, and who have support to maintain that literacy, are at the very least able to maintain and master their first language.  There are differences between those who learn a language in a class environment and those who learn through total immersion, usually living in a country where the target language is widely spoken. Without the possibility to actively translate, due to a complete lack of any first language communication opportunity, the comparison between languages is reduced. The new language is almost independently learned, like the mother tongue for a child, with direct concept-to-language translation that can become more natural than word structures learned as a subject. Added to this, the uninterrupted, immediate and exclusive practice of the new language reinforces and deepens the attained knowledge.

International Journal of Bilingualism International Journal of Bilingualism International Symposium on BilingualismInternational S

Look up multilingual,multilingualism, bilingual, or bilingualism in Wiktionary, the free dictionary.

Wikimedia Commons has media related toMultilingualism.

• ESRC Centre for Research on Bilingualism in Theory and Practice

• Cultural diversity
• List of multilingual countries and regions
• Plurilingualism
• Code-switching
• Translanguaging

• European Commissioner for Multilingualism
• European Day of Languages
• English-only movement
• Language legislation in Belgium
• Languages of Finland
• Languages of the European Union
• Multilingualism in Luxembourg
• Official bilingualism in Canada

• Language education

• Bilingual name
• Bilingual sign
• Childhood Bilingualism Research Centre (in Hong Kong)
• Economics of language
• Linguapax Prize
• List of artworks known in English by a foreign title
• Spanish language in the United States
• The Multilingual Library
• Category:Multilingual broadcasters