Johannessen focuses on coordination, i.e. structures with conjunctions such as and, but, and or. These are important words in their constructions because they have many properties in common with categories like verbs and prepositions. She has analyzed thirty-three languages and has found many striking similarities, presenting the first study of coordination from a cross-linguistic perspective. Her theory of syntactic coordination aims to be general and universal, and is broadly compatible with Chomsky's minimalist framework.