Multilingualism can be understood as an individual or a social phenomenon. It can refer to the acquisition, knowledge or use of several languages by individuals or by language communities in a speciﬁc geographical area. What is the relationship between multilingualism and applied linguistics? Research in applied linguistics deals with real-world problems related to language. As Auer and Li (2007) point out, multilingualism is not a problem in itself but a traditional monolingual view has seen multilingualism as a problem. In this chapter we consider that multilingualism is a powerful resource for individuals and societies. Multilingualism is not a new phenomenon because there has always been contact between speakers of diﬀerent languages related to commerce, wars, or immigration. Multilingual individuals, such as Cardinal Giuseppe Caspar Mezzofanti (1774-1849) who spoke almost forty languages, are admired, and speaking languages has traditionally been associated with a high level of education. Nowadays, globalization has spread the use of English all over the world to a greater extent than any other language in the past, and English is increasingly used as a lingua franca, along with many other languages. At the same time, in many parts of the world there is a growing interest in maintaining and developing other languages such as Quechua or Aymara in South America or Basque, Welsh or Frisian in Europe. As Franceschini (2009) points out, the study of multilingualism, a term which is increasingly used to address diﬀerent forms of language acquisition and language use, has had an important development in the last two decades. Multilingualism is related to many areas of applied linguistics and therefore to many other
chapters in this volume. This chapter will focus on diﬀerent aspects of multilingualism, including cognitive issues such as the outcomes of multilingualism, language processing in multilinguals, multilingualism and age, and the acquisition of additional languages. It also includes socioeducational issues such as language planning and education, multilingual identities, multilingual practices, multilingualism in the linguistic landscape and multimodality.