The elements in a literary work used to evoke mental images, not only of the visual sense, but of sensation and emotion as well. While most commonly used in reference to figurative language, imagery is a variable term which can apply to any and all components of a poem that evoke sensory experience and emotional response, whether figurative or literal, and also applies to the concrete things so imaged.
Sidelight: Imaginative diction transfers the poet's impressions of sight, sound, smell, taste and touch to the careful reader, as in "The Chambered Nautilus," by Oliver Wendell Holmes, or "The Cloud," by Percy Bysshe Shelley.
Sidelight: In addition to its more tangible initial impact, effective imagery has the potential to tap the inner wisdom of the reader to arouse meditative and inspirational responses.
Sidelight: Related images are often clustered or scattered throughout a work, thus serving to create a particular tone. Images of disease, corruption, and death, for example, are recurrent patterns shaping the tonality of Shakespeare's Hamlet. Imagery can also emphasize a theme, as do the suggestions of dissolution, depression, and mortality in John Keats' "Ode to a Nightingale."
(See also Ekphrasis, Figure of Speech, Trope)

This definition is in context to Poetry. See more contextual defintions for Imagery, Image.