Poetic diction is the term used to refer to the linguistic style, the vocabulary, and the metaphors used in the writing of poetry. In the Western tradition, all these elements were thought of as properly different in poetry and prose up to the time of the Romantic revolution, when William Wordsworth challenged the distinction in his Romantic manifesto, the Preface to the second (1800) edition of Lyrical Ballads (1798). Wordsworth proposed that a "language near to the language of men" was as appropriate for poetry as it was for prose. This idea was very influential, though more in theory than practice: a special "poetic" vocabulary and mode of metaphor persisted in 19th century poetry. It was deplored by the Modernist poets of the 20th century, who again proposed that there is no such thing as a "prosaic" word unsuitable for poetry.

Poetry, also called verse, is a form of literature that uses aesthetic and often rhythmic qualities of language − such as phonaesthetics, sound symbolism, and metre − to evoke meanings in addition to, or in place of, a prosaic ostensible meaning. A poem is a literary composition, written by a poet, using this principle.