Chapter 15 opens by asking readers to work through a complex language analysis problem, where the solution requires figuring out what the component parts mean and then making new sentences with those parts. This exercise introduces the notion of scaffolding, which goes beyond the advice that given information should precede new information. The progression from one type of information to the other will likely involve multiple steps, and attention to the order of each step should ideally be audience specific. The chapter encourages readers to describe their topics with as much technical apparatus as they want and then to break their descriptions down as much as possible. An example with vowel formants is introduced, emphasizing links back to problems with jargon and to the idea that incomplete is not incorrect. The Worked Example describes scaffolding in the formant example for the levels of explanation one might use for a young child, an older child, a teenager, a college student, and someone with expertise in a language-related field. Technical terms, materials (such as videos, spectrogram-making programs, or diagrams), and take-home messages are modified accordingly.

This chapter provides an overview of research on heritage language (HL) sound systems, with a focus on areas of convergence and divergence among heritage speakers (HSs), native speakers (NSs) who continue to be dominant in the language, and second language learners (L2ers) who acquired the language later in life. Drawing on data from a wide range of HLs, the chapter addresses both phonetic (articulatory, acoustic, perceptual) and phonological (phonemic, distributional, phonotactic) aspects of the HL sound system, as well as that of the majority language, in light of theories of bilingual speech and variables previously studied as predictors of HSs’ linguistic behavior. Despite the diversity of results reviewed, several recurring themes emerge, including intermediate patterning between NSs and L2ers, a higher level of performance in perception than production, and individual variability. In particular, the depth and the accessibility of HSs’ knowledge of the HL sound system show considerable variation related to structural linguistic factors, demographic and sociolinguistic factors, input and usage-based factors, and methodological factors. In addition to summarizing the areas in which there is an emerging consensus, the chapter points out a number of remaining questions that pave the way for future research on HL sound systems.