It’s estimated that half the world’s population is bilingual, and two-thirds of the world’s children grow up in an environment where several languages intersect. But while bilingualism is common, its definitions are varied. They are often based on people’s experiences or feelings about language – what they convey and what they represent.
The question also divides linguists. While some emphasise cultural integration as the most important factor, others say that only an individual with equivalent mastery of both languages can truly be considered bilingual.
In 1930, linguist Leonard Bloomfield defined bilingualism as the complete control of two languages, as if each were a mother tongue. This is an idealised vision of a perfect, balanced bilingualism, assuming equivalent written and oral skills in both languages. According to this definition, a bilingual speaker is the sum of two monolinguals. However, this type of bilingualism is extremely rare, and in reality, bilingual people have varied language profiles. Each is unique in their relationship to language.
There are other theories of bilingualism. The Canadian linguist William F Mackey defines it as the alternating use of two or more languages, while Swiss scholar François Grosjean argues that people who are bilingual use two or more languages in their everyday activities. Vivian Cook, from the UK, defines a bilingual person as a multi-skilled individual who develops language skills consistent with the context of acquisition and use of the second language. Thus, an individual may be considered bilingual even if he or she has only a partial command of the second language.
Where does that leave us? Today, a working definition of bilingualism would correspond to the regular and alternating use of at least two languages by an individual – a category that applies to several million speakers.