Poetry has a long history, dating back to the Sumerian Epic of Gilgamesh. The earliest poems evolved from folk songs, such as the Chinese Shijing, or from the need to retell oral epics, such as the Sanskrit Vedas, Zoroastrian Gathas, and the Homeric epics, the Odyssey and the Iliad. Ancient attempts to define poetry, such as Aristotle's Poetics, focused on the uses of speech in rhetoric, drama, song, and comedy. Later attempts concentrated on features such as repetition, verse form and rhyme, and emphasized the aesthetics which distinguish poetry from more objectively informative, prosaic forms of writing, such as manifestos, biographies, essays, and novels . From the mid-20th century, poetry has sometimes been more generally labeled as a fundamental creative act using language.
Poetry primarily is governed by idiosyncratic forms and conventions to suggest differential interpretation to words, or to evoke emotive responses. Devices such as assonance, alliteration, onomatopoeia, and rhythm are sometimes used to achieve musical or incantatory effects. The use of ambiguity, symbolism, irony, and other stylistic elements of poetic diction often leaves a poem open to multiple interpretations. Similarly, metaphor, simile, and metonymy create a resonance between otherwise disparate images--a layering of meanings, forming connections previously not perceived. Kindred forms of resonance may exist, between individual verses, in their patterns of rhyme or rhythm.
Some poetry types are specific to particular cultures and genres, responding to the characteristics of the language in which the poet writes. Readers accustomed to identifying poetry with Dante, Goethe, Mickiewicz and Rumi may think of it as being written in lines based upon rhyme and regular meter, there are traditions, such as Biblical poetry, that use other methodologies to create rhythm and euphony. Much of modern British and American poetry is to some extent a critique of poetic tradition, playing with and testing (among other things) the principle of euphony itself, to the extent that sometimes it deliberately does not rhyme or keep to set rhythms at all. In today's globalized world poets often borrow styles, techniques and forms from diverse cultures and languages.