Drawing on a far-flung, multilingual archive of contracts and financial instruments from around the western Indian Ocean, this article highlights how cross-cultural trade depended on the ability of groups to translate between one system and another, rendering one commercial lexicon legible to another so as to produce commensurability and allow for conversions to take place. Law constituted a foundational building block of this process: Indian Ocean merchants drew on a deep well of legal concepts and forms as they attempted to make their worlds legible to one another, mobilizing the grammars of law to bridge commercial systems. We situate these dynamics within the context of the Indian Ocean ‘bazaar’, establishing it as a site for thinking about the place of cross-cultural trade in world history, and the histories of global capitalism more broadly. We suggest that Euro-American capitalism’s very agents had to adapt their commerce to the idioms, logics, and contracts of their business partners around the Indian Ocean – a vernacular world of the bazaar that was itself already in motion.