This introduction to the volume provides background on common themes that appear across its chapters. First, it contextualizes the notions of heritage languages and heritage speakers before providing reasons why research on heritage sound systems has lagged behind work on other linguistic areas. It then offers an overview of what we have discovered to date about heritage sound systems, while also pointing out gaps and topics that merit further exploration. Motivated by the discussion in the first portion of this piece, the latter half covers the breadth, goals, and novel aspects of the current volume before providing brief summaries of the empirical studies carried out in each of its seventeen chapters.

This chapter provides an introductory overview of the phonological systems used in the languages of mainland Southeast Asia. The chapter begins with an overview of the various systems of consonants and vowels that are found, and the phonotactic principles by which those segments are combined to form syllables. The closely-related phenomena of register and tone are then introduced and defined, followed by an outline of the processes of tonogenesis, by which a language can develop a tone system. The chapter closes with a discussion of further aspects of the area’s sound systems, including tone sandhi, intonation, the prosodic hierarchy and criteria for different notions of ‘word’.