A visual language is a system of communication using visual elements. Speech as a means of communication cannot strictly be separated from the whole of human communicative activity that includes the visual and the term 'language' in relation to vision is an extension of its use to describe the perception, comprehension and production of visible signs.
An image that dramatizes and communicates an idea presupposes the use of a visual language. Just as people can 'verbalize' their thinking, they can 'visualize' it. A diagram, a map, and a painting are all examples of uses of visual language. Its structural units include line, shape, color, form, motion, texture, pattern, direction, orientation, scale, angle, space and proportion.
The elements in an image represent concepts in a spatial context, rather than the linear form used for words. Speech and visual communication are parallel and often interdependent means by which humans exchange information.
Visual units in the form of lines and marks are constructed into meaningful shapes and structures or signs. Different areas of the cortex respond to different elements such as colour and form. Semir Zeki had shown the responses in the brain to the paintings of Michaelangelo, Rembrandt, Vermeer, Magritte, Malevich and Picasso.
What we have in our minds in a waking state and what we imagine in dreams is very much of the same nature. Dream images might be with or without spoken words, other sounds or colours. In the waking state there is usually, in the foreground, the buzz of immediate perception, feeling, mood and as well as fleeting memory images. In a mental state between dreaming and being fully awake is a state known as 'day dreaming' or a meditative state, during which "the things we see in the sky when the clouds are drifting, the centaurs and stags, antelopes and wolves" are projected from the imagination. Rudolf Arnheim has attempted to answer the question: what does a mental image look like? In Greek philosophy, the School of Leucippus and Democritus believed that a replica of an object enters the eye and remains in the soul as a memory as a complete image. Berkeley explained that parts, for example a leg rather than the complete body, appear in the mind. Arnheim considers the psychologist, Edward B. Titchener's account to be the breakthrough in understanding something of how the vague incomplete quality of the image is 'impressionistic' and carries meaning as well as form.