The aim of this paper is to identify and systematize the functions of clearly in academic discourse. The adverb shows a continuum of manner and modal meanings, and signals the existence of reliable evidence for claims, which makes it a useful rhetorical device in research articles. The study is based on a corpus of 80 research articles (ca. 580,000 words) representing three disciplines and three branches of science: linguistics (the humanities), sociology (social sciences) and physics (natural sciences). It shows that clearly is used to involve the reader in the process of data analysis (both manner and modal uses), to summarize the findings, make conclusions (modal uses), and to appeal to shared knowledge (discourse marker). Appeals to shared knowledge are only attested in the subcorpora of linguistics and sociology, which tend to adopt a more interactional style of writing than the natural sciences, while the other functions are found in the research articles of all three disciplines. Using White’s (2003) notion of heteroglossic (dis)engagement, clearly can be said to have dialogically contractive functions. Its presence in the text indicates the author’s wish to encourage the reader to adopt his/her perspective.