For all students, it is important to see that researchers use a wide variety of definitions of individual bilingualism. There are very strict and very demanding psycholinguistic definitions, such as Bloomfield's (1933) claim that a bilingual should possess "native-like control of two or more languages". Others, such as Weinreich (1953) and Grosjean (1997) propose definitions that are based on language use rather than language competence. Before showing students the range of definitions of bilingualism, it can be very helpful to ask them to formulate their own definition in writing. Students can subsequently collect these definitions and discuss them in class. This often leads students to formulate very original views on the issue and it generates an interest in the definitions given by the experts in the field, which are to be presented and discussed subsequently.
A bilingual individual, generally, is someone who speaks two languages. An ideal or balanced bilingual speaks each language as proficiently as an educated native speaker. This is often referred to as an ideal type since few people are regarded as being able to reach this standard. Otherwise, a bilingual may be anywhere on a continuum of skills.
Literacy abilities may be an additional dimension to bilingualism, but they are often referred to separately as biliteracy, leaving bilingualism to carry the weight of oral language abilities. Bilingualism is a specific case of multilingualism, which has no ceiling on the number of languages a speaker may dominate. The timing and sequence in which one learns each of the languages has led to other distinctions between kinds of multilingualism. Much of the linguistics literature, for example, identifies native language or mother tongue as a first language, ignoring the possibility or diminishing the value of having more than one native language or mother tongue. Such a person is often referred to as a simultaneous bilingual, while someone who acquires the second language after the first one is often referred to as a sequential bilingual ("early" if between early childhood and puberty, and "late" if after puberty). The context of language acquisition leads naturally to distinguishing between "informal" bilinguals, who acquire their languages outside of formal settings like schools, imitating the natural processes of acquiring the mother tongue, and "formal" bilinguals, who generally learn the language in schools or similar settings.
When these terms apply to groups, one speaks of bilingual or multilingual communities or nations. The aggregate enumeration of the speakers in these groups (also referred to as language diversity or demography) will often profile the number of monolingual and bilingual speakers of each language. For example, there may be a multilingual community in which speakers are monolingual in each of three languages. This would be rare, and the language groups would probably be isolated from each other. More often than not, a multilingual community or nation has multilingual individuals. If the situation involves social or political power, then a language group may be referred to as a language minority (minority-language) group or a language majority (majority-language) group, reflecting the power relationship to other groups in the society or political unit.