Multilingualism...

The term multilingualism can refer to an occurrence regarding an individual speaker who uses two or more languages, a community of speakers where two or more languages are used, or between speakers of different languages.

A multilingual person, in the broadest definition, is anyone who can communicate in more than one language, be it active (through speaking and writing) or passive (through listening and reading). A generic term for multilingual persons is polyglot.

Multilingual speakers have acquired and maintained at least one language during childhood, the so-called first language. First languages (sometimes also referred to as mother tongue) are acquired without formal education, by mechanisms heavily disputed. Children acquiring two first languages since birth are called simultaneous bilinguals. Even in the case of simultaneous bilinguals one language usually dominates over the other. This kind of bilingualism is most likely to occur when a child is raised by bilingual parents in a predominantly monolingual environment. It can also occur when the parents are monolingual but have raised their child or children in two different countries.

Potential multilingual speakers
People with a strong interest in a foreign language.
People who find it necessary to acquire a second language for practical purposes such as business, information gathering (Internet, mainly English) or entertainment (foreign language films, books or computer games).
Language immersion children.
Immigrants and their descendants. Although the heritage language may be lost after one or two generations particularly if the replacing language has greater prestige.
Children of expatriates. However, language loss in younger children may be rapid when removed from a language community.
Residents in border areas between two countries of mixed languages where each language is seen of equal prestige. Yet, in areas where one language is more prestigious than the other, speakers of the less prestigious language may acquire the dominant language. In time, however, the different language communities may likely become one, as one language becomes extinct in that area.
Children whose parents each speak a different language, in multilingual communities. In unilingual communities, when parents maintain a different-parent/different-language household, younger children may appear to be multilingual, however, entering school will overwhelm the child with pressure to conform to the dominant community language. Younger siblings in these households will almost always be unilingual. On the other hand, in unilingual communities, where parents have different native languages, multilingualism in the child may be achieved when both parents maintain a one-language (not the community language) household.
Children in language-rich communities where neither language is seen as more prestigious than the other and where interaction between people occurs in different languages on a frequent basis.
Children who have one or more parents who have learned a second language, either formally (in classes) or by living in the country. The parent chooses to speak only this second language to the child.

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