When people talk, they recruit a wide range of expressive devices for interactional work, from sighs, sniffs, clicks, and whistles to other conduct that borders on the linguistic. These resources are used in the management of turn and sequence and the marking of stance and affect, and they represent an aspect of the interactional machinery that is as elusive as it is powerful. Phenomena long assumed to be beyond the purview of linguistic inquiry emerge as systematically deployed practices whose ambiguous degree of control and convention allows participants to carry out subtle interactional work without committing to specific words. While these resources have been characterized as nonlexical, nonverbal, or nonconventional, I propose that they are unified in their liminality: They work well precisely because they equivocate between sound and speech. The empirical study of liminal signs shows the promise of sequential analysis for building a science of language on interactional foundations.Physiologically, speech is an overlaid function, or, to be more precise, a group of overlaid functions. It gets what service it can out of organs and functions, nervous and muscular, that have come into being and are maintained for very different ends than its own. (Sapir, 1921, p. 8) Everyday language use is full of sighs, sniffs, whistles, clicks, and other conduct that borders on the linguistic. For a long time, these sounds and actions have escaped analytical attention. One reason is technological: Recording and transcription methods were not up to the task. Another is theoretical: A focus on idealized competence led a generation of linguists to look away from what was seen as the flotsam and jetsam of mere performance. But the most intriguing reason is delightfully self-referential: For talk-in-interaction to work as smoothly as it does, perhaps some aspects of it must seem like not-talk.The articles in this issue move the goalposts of research on language in social interaction in three ways. They showcase new affordances of technology and transcription that bring new areas within reach of systematic scrutiny. They respecify conceptual foundations to call into question received views on what is and isn't linguistic. And they bring into view some of the more elusive aspects of language in everyday use. The interactional resources we encounter here emerge as integral elements of an interactional machinery that is "finely powerful" (McHoul, 2005, citing Harvey Sacks's unfinished book) and that underpins the most sophisticated uses of language.