This book presents one of the first attempts at developing a precise, grammatically rooted, theory of conversation motivated by data from real conversations. The theory has descriptive reach from the micro-conversational -- e.g. self-repair at the word level -- to macro-level phenomena such as multi-party conversation and the characterization of distinct conversational genres. It draws on extensive corpus studies of the British National Corpus, on evidence from language acquisition, and on computer simulations of language evolution. The theory provides accounts of the opening, middle game,...