This article provides a comprehensive account of the lexical and terminological essence of ʿilm al-bayān (the science of bayān). The study analyzes the Arabic origin of the term bayān, its meanings associated with clarity and explicitness, and examines it through the views of early Arab scholars—Jahiz, Rumoniy, and Abdulqohir Jurjoniy. The article also discusses the place of bayān within the science of rhetoric (balāgha) and explains in detail the types of dalāla (modes of signification) used to express meanings: verbal expression (lafz), gesture (ishora), contract (aqd), writing (xat), and situational context (holat). In addition, the paper outlines—on a scholarly basis—the set of knowledge and skills that a practitioner of bayān must possess, as indicated by Ibn al-Asir. The research reveals the important role of ʿilm al-bayān in ensuring clarity of speech, artistic expression, and rhetorical eloquence.