Many grammatical frameworks view words and rules as the basic building blocks of language, with multiword sequences being treated as peripheral exceptions in the form of idioms, etc.. The new millennium, however, has seen a shift toward construing multiword sequences not as linguistic rarities but as important building blocks for language acquisition and processing. Based on a growing bulk of evidence of sensitivity to multiword sequences in language learning and use, multiword sequences have come to figure prominently in many current approaches to language, including item-based learning, formulaic language, usage-based language processing, and chunk-based learning. This symposium brings together experts from these different approaches to language to explore the idea that first and second language learners differ with respect to their ability to use multiword building blocks to learn and process language, and that this difference affects learning strategies and outcomes.