The study of how the visual and verbal choices themselves are the message. An academic discipline with its own accredited undergraduate curriculum.

Communication design sits at the intersection of graphic design and rhetoric: it treats typography, colour, layout, and imagery as carrying meaning in their own right. The academic grounding for this is social semiotics, Gunther Kress’s multimodality theory treats images, layout, and text as parallel “modes” that jointly construct meaning, treating writing and visuals as primary illustration.

Source (theoretical foundation): Forceville, C. “Multimodality: A Social Semiotic Approach to Contemporary Communication” (review of Kress), Journal of Pragmatics, 2011.