Book excerpt: Frequency has been identified as one of the most influential factors in language processing, and plays a major role in usage-based models of language learning and language change. The research presented in this volume challenges established models of linguistic representation. Instead of learning and processing language compositionally, larger units and co-occurence relations are at work. The main point taken by the authors is that by studying the effect of distributional patterns and changes in such patterns we can establish a unified framework that explains the dynamics of language systems with a limited set of processing factors.