Coming from the Latin forma, implying beauty, the word 'Form' is more commonly related to the definitions an usage of the Latin eidos, originally signifying recognizable visual characteristics of a thing -- perceptible characteristics such as shape; the meaning was eventually expanded to characteristic nature, type, a cognitive constant having the recognizability and intelligibility as a distinct entity; and then to internal spatial and other relationships between shapes. It should be noted that this latter definition of internal form between shapes leads to the notion of a form within a form, as the original interpretation of eidos is 'shape'.
Plato conceived of eidos as the perceptible and sensible characteristics of a thing, and used the word to describe concrete shape. These shapes, then became engulfed in Socratic discussions of representation and imitation and what he considered to be their inherent deception and falsity. Aristotle, however, linked form to cause, essence, and identity to draw the idea that a substance, the primary type of being, and something on which beings depend, persists as long as the form of the substance persists. Aristotle also believed that form is irreducible to matter, and material composition does not constitute being. Although there is a definite contrast between form and matter, they are closely related, as forms may be part of or made up of matter. He had notions of two kinds of substantial form, the species form, the physical form shared by members of a species, or a particular form , the Socratic sense of the word. Supporters of the species form, or 'universal solution' emphasize the contrasting of form, and the form and matter complex, and the classification of particulars as compounds, and therefore not forms. Supporters of the 'particular solution' note that no universal can be a substance, which must be a subject, and is also a particular.
Ferdinand de Saussure approached form from the 'internal relationships' sense and came out with a notion of extreme external form. Using language as his target, he discussed 'the form of the language' as the differing of signs between languages to represent the same thing, and concluded that language is form. He also noted that language, as form, involves expression, content, and nomenclature, bringing yet another level of internal form into the picture. In this way, Saussure developed both the internal and external aspects of the form of language, and, in the end, found that the external form and internal form coincide - though signs within language have not only original formal relationships with one another, but also formal characteristics to distinguish themselves, they are entirely dependent on the form of the language, which is, simultaneously, form.
Clement Greenberg brought about the first principles of what became known as formalism with his numerous writings on the emergence of modern art in America in the 1930s and 1940s. Formalism in art is the notion that a work's artistic value is entirely determined by its form. However, because notions of 'artistic form' tend to vary, this doctrine of formalism varies with it. Greenberg began by placing the value of modern art on form, conceiving of 'art form' as achieved by eliminating representational and illusionistic aspects of a work and replacing them with aspects of the work's internal identity. He further addressed this placement of artistic value by noting that defining a work of art by the art form, or medium, it represents results in an auto-isolation of the work in its medium, and the limiting of its artistic possibilities to the nature of it's medium, while at the same time proving the ability to hold its own value. The outcome of this self-criticism and defining of boundaries was a separation of the art forms that had succeeded in merging during and after impressionism. This earlier merging resulted in a 'confusion of the arts', which ultimately spurred the segregation. According to Greenberg, the 'confusion of the arts' resulted in a lack of purity, and following this, he sees abstraction to be the purest art of all.
Another instance of the formalistic internal form of a work of art defining the entire work is discussed by Michael Fried. Fried classified sculptures into those which are 'art' and those which are demonstrative of ' objecthood '. To be 'art' the work had to demonstrate a clear composition of parts in which shape is independent from, and clearly defined without, the object. Works which blurred the lines of subject and object, structure and content, even audience and work, and especially medium and subject he considered examples of 'objecthood'. The 'objecthood' category incorporated the minimalist works that are known for challenging the boundaries of art in a very deliberate way.
What was represented by the word 'form' in the earlier twentieth century is now known as 'structure', a change that occurred with the evolution of European structuralism. In this evolution, the structuralists began using the word 'structure', which had previously described relationships between elements, to differentiate from the philosophical definition of form, connotating mental capabilities and processes. Previously indicative of transcendental essence, the metaphysical, the ontological, and the generally idealist view of knowledge as stemming from mental processes, 'form' was used interchangeably with 'structure' in the 1930s and '40s by Anglo-American New Critics to describe properties of artwork and also the essence of the aesthetic experience.
Currently, there are three approaches to form, all of which are used with mostly neutral attention. The first is the Platonic, classical definition: collection of perceptible elements which can incorporate the Socratic and Benjaminian ideas of representation and its false implications resulting from mediation, reproduction, interpretation, and translation. The second is the Aristotelian definition: intelligible elements of nature, kind, or type, impressionistic? The third is the modernist approach of internal form in association with and contrasting with external form, and especially the formalist principle of a work's form determining its value as art. Used in combination, these notions are interplayed in media theory to combine formal artistic analysis of composition, consideration of aesthetic value, and relations between mediums or forms of art, on a common term.