Poetry is a form of literature that uses aesthetic and rhythmic qualities of language—such as phonaesthetics, sound symbolism, and metre—to evoke meanings in addition to, or in place of, the prosaic ostensible meaning.Poetry has a long history, dating back to the Sumerian Epic of Gilgamesh. Early poems evolved from folk songs such as the Chinese Shijing, or from a need to retell oral epics, as with the Sanskrit Vedas, Zoroastrian Gathas, and the Homeric epics, the Iliad and the Odyssey. 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. From the mid-20th century, poetry has sometimes been more generally regarded as a fundamental creative act employing language.Poetry uses 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 figures of speech such as 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 and respond to 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 written in lines based on rhyme and regular meter; there are, however, traditions, such as Biblical poetry, that use other means to create rhythm and euphony. Much modern poetry reflects a critique of poetic tradition, playing with and testing, among other things, the principle of euphony itself, sometimes altogether forgoing rhyme or set rhythm. In today's increasingly globalized world, poets often adapt forms, styles and techniques from diverse cultures and languages.