This groundbreaking study of the morphology of comparison yields a surprising result: that even in suppletion (the wholesale replacement of one stem by a phonologically unrelated stem, as in good-better-best) there emerge strikingly robust patterns, virtually exceptionless generalizations across languages. Jonathan David Bobaljik describes the systematicity in suppletion, and argues that at least five generalizations are solid contenders for the status of linguistic universals. The major topics discussed include suppletion, comparative and superlative formation, deadjectival verbs, and lexical decomposition. Bobaljik’s primary focus is on morphological theory, but his argument also aims to integrate evidence from a variety of subfields into a coherent whole. In the course of his analysis, Bobaljik argues that the assumptions needed bear on choices among theoretical frameworks and that the framework of Distributed Morphology has the right architecture to support the account. In addition to the theoretical implications of the generalizations, Bobaljik suggests that the striking patterns of regularity in what otherwise appears to be the most irregular of linguistic domains provide compelling evidence for Universal Grammar. The book strikes a unique balance between empirical breadth and theoretical detail. The phenomenon that is the main focus of the argument, suppletion in adjectival gradation, is rare enough that Bobaljik is able to present an essentially comprehensive description of the facts; at the same time, it is common enough to offer sufficient variation to explore the question of universals over a significant dataset of more than three hundred languages.