Multimodality is the application of multiple literacies within one medium. Multiple literacies or "modes" contribute to an audience's understanding of a composition. Everything from the placement of images to the organization of the content to the method of delivery creates meaning. This is the result of a shift from isolated text being relied on as the primary source of communication, to the image being utilized more frequently in the digital age. Multimodality describes communication practices in terms of the textual, aural, linguistic, spatial, and visual resources used to compose messages.

While all communication, literacy, and composing practices are and always have been multimodal, academic and scientific attention to the phenomenon only started gaining momentum in the 1960s. Work by Roland Barthes and others has led to a broad range of disciplinarily distinct approaches. More recently, rhetoric and composition instructors have included multimodality in their coursework. In their position statement on Understanding and Teaching Writing: Guiding Principles, the National Council of Teachers of English state that "'writing' ranges broadly from written language (such as that used in this statement), to graphics, to mathematical notation."

Although multimodality discourse mentions both medium and mode, these terms are not synonymous. However, they may overlap depending on how precisely (or not) individual authors and traditions use the terms.

Gunther Kress's scholarship on multimodality is canonical with social semiotic approaches and has considerable influence in many other approaches, such as in writing studies. Kress defines 'mode' in two ways. One: a mode is a type of material resource that is socially or culturally shaped to make meaning. Images, writing, speech and gesture are all examples of modes. Two: modes are semiotic, shaped by intrinsic characteristics and their potential within their medium, as well as what is required of them by their culture or society.

Thus, every mode has a distinct historical and cultural potential and or limitation for its meaning. For example, if we broke down writing into its modal resources, we would have grammar, vocabulary, and graphic "resources" as the acting modes. Graphic resources can be further broken down into font size, type, color, size, spacing within paragraphs, etc. However, these resources are not deterministic. Instead, modes shape and are shaped by the systems in which they participate. Modes may aggregate into multimodal ensembles and be shaped over time into familiar cultural forms. A good example of this is films, which combine visual modes (in setting and in attire), modes of dramatic action and speech, and modes of music or other sounds. Studies of multimodal work in this field include van Leeuwen; Bateman and Schmidt; and Burn and Parker's theory of the Kineikonic Mode.

In social semiotic accounts, a medium is the substance in which meaning is realized and through which it becomes available to others. Mediums include video, image, text, audio, etc. Socially, a medium includes semiotic, sociocultural, and technological practices. Examples include film, newspapers, billboards, radio, television, a classroom, etc. Multimodality also makes use of the electronic medium by creating digital modes with the interlacing of image, writing, layout, speech, and video. Mediums have become modes of delivery that consider the current and future contexts.

Multimodality (as a phenomenon) has received increasingly theoretical characterizations throughout the history of communication. Indeed, the phenomenon has been studied at least since the 4th century BC, when classical rhetoricians alluded to it with their emphasis on voice, gesture, and expressions in public speaking. However, the term was not defined with significance until the 20th century. During this time, an exponential rise in technology created many new modes of presentation. Since then, multimodality has become standard in the 21st century, applying to various network-based forms such as art, literature, social media and advertising. The monomodality, or singular mode, which used to define the presentation of text on a page has been replaced with more complex and integrated layouts. John A. Bateman says in his book Multimodality and Genre, "Nowadays… text is just one strand in a complex presentational form that seamlessly incorporates visual aspect 'around,' and sometimes even instead of, the text itself." Multimodality has quickly become "the normal state of human communication."

During the 1960s and 1970s, many writers looked to photography, film, and audiotape recordings in order to discover new ideas about composing. This led to a resurgence of a focus on the sensory, self-illustration known as expressionism. Expressionist ways of thinking encouraged writers to find their voice outside of language by placing it in a visual, oral, spatial, or temporal medium. Donald Murray, who is often linked to expressionist methods of teaching writing once said, "As writers it is important that we move out from that which is within us to what we see, feel, hear, smell, and taste of the world around us. A writer is always making use of experience." Murray instructed his writing students to "see themselves as cameras" by writing down every single visual observation they made for one hour. Expressionist thought emphasized personal growth, and linked the art of writing with all visual art by calling both a type of composition. Also, by making writing the result of a sensory experience, expressionists defined writing as a multisensory experience, and asked for it to have the freedom to be composed across all modes, tailored for all five senses.