Thank you for using the Jiskha Homework Help Forum. A definition that appeals to me most for "poetry" "says as much as possible with few words." Therefore the poet carefully selects the words most carefully to convey the "message" of the poem = the thoughts, emotions, etc. Literary devices deepen the meaning with symbols, metaphors, similes, etc. To my way of thinking, poetry MUST be read aloud to enjoy the assonance, alliteration, rhyme, etc. The devices are only "tools" and it is up to the poet to select the best ones.
So, select a poem, look at and listen to the structure, shape, "music" in it.
In "The Tyger" Poem
What does the author mean with this phase? And what shoulder, & what art,
Could twist the sinews of thy heart?
And when thy heart began to beat,
What dread hand? & what dread feet?