The term "concrete poetry" was first used in the 1950s to describe a type of verse traditionally called "pattern" or "shape" poetry, in which the poem's appearance on the page visually suggested the theme or subject. Scandinavian and Brazilian poets of this period experimented with new ways to compose these poems, bringing the concept of the concrete poem to new audiences and finding innovative ways to link form and meaning.
Most poetry is highly flexible, with fewer limitations on syntax, structure and form than prose works which primarily depend on two forms, sentence and paragraph. Poets can take advantage of this flexibility to add a visual dimension to the work, and many poems show choices in line arrangement and stanza structure for emphasis or theme. The poems of e.e.cummings, for example, use spacing, letter arrangement and line length to reflect the main theme.
Concrete poetry takes the flexibility of poetry a step further, establishing a visual shape on the page which clearly echoes or supports the theme. A poem about love could be written in the shape of a heart, or a verse about snakes might wind sinuously across the page. Letters and words can also be used to support the theme. For example, a feeling of slowness can be visually depicted with more vowels and spaces in the word "s l o o o w."
The general category of concrete poetry has two subtypes. Visual poetry is an arrangement of text and visual elements that can also include symbols and images. Haptic poetry combines typography with three-dimensional art forms such as sculpture to create a work that can be touched as well as seen and read. Poets as diverse as Lewis Carroll, Robert Frost and George Herbert have produced works of concrete poetry; this form is also widely used in poetry for children.