The arrangement or method used to convey the content, such as free verse, ballad, haiku, etc. In other words, the "way-it-is-said." A variably interpreted term, however, it sometimes applies to details within the composition of a text, but is probably used most often in reference to the structural characteristics of a work as it compares to (or differs from) established modes of conventionalized arrangements.
Sidelight: The form of a poem which follows a set pattern of rhyme scheme, stanza form, and refrain (if there is one), is called a fixed form, examples of which include: ballade, limerick, pantoum, rondeau, sestina, sonnet, triolet, and villanelle. Used in this sense, form is closely related to genre.
Sidelight: While familiarity and practice with established forms is essential to learning the craft, a poet needn't be slavishly bound by them; a great poet masters techniques, experiments, and extends his or her imaginative creativity to new boundaries.
(Compare Diction, Motif, Persona, Style, Texture, Tone)

This definition is in context to Poetry. See more contextual defintions for Form.