This book unsettles regular accounts of knowledge about language in several ways. The idea of assemblages allows for a flexibility about what languages are, not just in terms of having fuzzy linguistic boundaries but in terms of what constitutes language more generally. Languages are assembled from different elements, both linguistic elements as traditionally understood as well as items less commonly included. This is to approach language not as a pre-existing or circumscribed entity but rather as something produced in social action. Language from this point of view is embedded in diverse social and physical environments, distributed across the material world and part of our embodied existence. Once we ask whose version of language counts, we have to base any practical theory of language on what language is within a local ontology. This necessitates an engagement with language ideological assemblages and an understanding that languages are inevitably locally made assemblages (linguistic, semiotic and material). Applied linguistics as a practical assemblage is one way we can start to address the needs for a practical theory of language that can remain both plural and political.