This book is an exploration of a very intriguing collection of linguistic beasts. Clitics is a fascinating subject. To study them adequately you really need to be concerned with all aspects of linguistics, from detailed phonetics to the analysis of discourse and conversation. Much of the interest they provoke is precisely because they sit at the interface between sound structure, word structure and sentence structure (not to mention the lexicon and language use). Partly for this reason, pinning down the notion of clitic is a little like trying to catch minnows with your bare hands. This has made it more difficult than usual to organize and arrange our material. In many cases it's hard to understand the point of, say, a phonological analysis of a set of clitics until you've seen the syntactic analysis of them, but without the phonological analysis it's difficult to understand the syntax. For this reason we've written some of the book cyclically, introducing some concepts at a basic level and returning to them later in the book to explore them in more detail. We've tried to reduce unnecessary overlap as far as possible but the reader will sometimes see similar examples cropping up in different places. In addition we've tried to perform a balancing act over choice of language examples. On the one hand it's important to see as much of the richness of clitics in the world's languages (and for us it's interesting to encounter or revisit many of those languages), but on the other hand it's much easier to understand some of the complexities of an unfamiliar language if you see it in several different contexts. For this reason we’ve tended to concentrate on languages that have been discussed a good deal in the literature, or with which we’re more or less familiar, or both.