This chapter provides an introduction to the Cambridge Handbook of Bilingual Phonetics and Phonology, and emphasizes the interdisciplinarity of the scholarship included in the Handbook, which contributes to the diversity of approaches, to theory-building, and to the collaborative connections that are enhancing the field. The abstracts of each of the thirty-five chapters are also included and are followed by concluding remarks providing a roadmap for the future of research on bilingual phonetics and phonology.

Heritage language speakers, or heritage speakers in short, are early sequential or simultaneous bilinguals whose home language, generally a diasporic or an indigenous language, differs from the majority language of the society. The goal of this chapter is to provide a comprehensive background of heritage speakers and their sound systems. It includes a literature review on the phonetics and phonology across heritage languages, particularly those of children of immigrants, in various majority language contexts. The chapter first describes heritage speakers and the general characteristics of their language learning experiences and outcomes. It then reviews studies examining heritage speakers’ global accent and factors contributing to perceived heritage accent. It also presents areas of divergence that have been found in the production and perception of heritage language segments and prosody. Lastly, the chapter synthesizes the findings, discussing common patterns observed in heritage language phonetics and phonology, and suggests areas for future research.