Why are kin, in societies all over the world, divided into “joking” and “avoidance” relations? Foundational figures in the human sciences, from E.B. Tylor and A.R. Radcliffe-Brown to Sigmund Freud and Claude Lévi-Strauss, have sought to explain why some classes of kin are normatively expected to prank and tease one another while others must studiously avoid each other’s presence. In this extensively researched comparative study, linguistic anthropologist Luke Owles Fleming offers a bold new answer to this problem. With a particular focus on avoidance relationships, On Speaking Terms argues that in order to understand cross-cultural convergences in the patterning of kinship-keyed comportments, we must attend to the sociolinguistic codes through which kinship relationships are enacted. Drawing on ethnographic data from more than one hundred different societies, the book documents and analyses parallels in the linguistic and non-verbal signs through which avoidance relationships are experientially realized. With dedicated discussions of Aboriginal Australian “mother-in-law languages,” name and word tabooing practices, pronominal honorification, and non-verbal strategies of interactional and sensorial avoidance, it reveals recurrent sociolinguistic patterns attested in kinship avoidance. In demonstrating the vital role of sociolinguistic codes for transforming kinship categories into phenomenologically rich relationships, On Speaking Terms makes an important contribution to the anthropology of kinship.