This chapter explores the critical and theoretical reach and power of Romanticism’s poetics by examining some of the words that its practitioners deploy to describe their own work. Romanticism takes everyday, even banal words and phrases and makes them its own, inflecting and redirecting them. In so doing, Romanticism invents itself as a radically new, iconoclastic, and dissident literary movement. Paying attention to this evolving lexical cluster allows us to discern emerging patterns within and connections between ideas and practices in the major intellectual and literary developments of the late eighteenth and early nineteenth centuries. It is in the production of a newly theorized aesthetic lexicon, and in the theorizing of this lexicon, that the definition or determination of what is called ‘Romanticism’ emerges. Romantic poetics, in other words, is the Romantic lexicon.