Metaphors and similes share some important attributes, and instructors often teach the terms alongside each other. Both simile and metaphor compare dissimilar objects or ideas as if they were closely related. Simile makes the comparison obvious by using the word "like" or "as" between the compared ideas. An example from John Steinbeck's "East of Eden" shows how simile adds color to language: "Kate inched over her own thoughts like a measuring worm." When a writer uses metaphor, as Sylvia Plath did in her poem about pregnancy, "Metaphors," the two objects or ideas are presented as the same. In her poem, Plath wrote: "I'm... an elephant, a ponderous house/ a melon strolling on two tendrils." People often confuse metaphors with personification, a figurative language form that assigns human characteristics to nonhuman things. A metaphor says the object actually is the other object; personification says the object has the characteristic: "Such is the indifference of heaven," wrote Victor Hugo in "Les Miserables." Hugo wasn't saying that the sky was actually indifference itself; the sky possessed indifference as a characteristic.
Hyperbole and understatement are two sides of the same figurative coin. Both figurative forms use emphasis to draw attention to the points they make, but hyperbole grossly overexaggerates the statement while understatement completely downplays it, often to the point of comedy. In his poem "The Concord Hymn," Ralph Waldo Emerson exaggerated the sound of a gunshot to communicate its importance: "Here once the embattled farmers stood/ And fired the shot heard round the world." J.D. Salinger employed understatement for its comedic value in this line from "The Catcher in the Rye": "It isn't very serious. I have this tiny tumor in my brain." Irony, while somewhat similar to hyperbole and understatement, takes the concept a step further by saying the opposite of what the writer means instead of understating or exaggerating it: in a well-known example of irony in "Julius Caesar," Shakespeare describes the murderous Brutus as "an honorable man."
Every part of writing uses symbols: letters are symbols for sounds, words are symbols for objects and objects are often symbols for ideas or themes. When a writer uses symbolism, he employs well-known symbols to add depth or extra meaning to the work. In her classic "The Bean Trees," Barbara Kingsolver used beans as a symbol to tell the reader something special about the newly adopted toddler Turtle; with nourishment and care, the bean vines grow into something worthwhile and beautiful despite their former existence as brittle, neglected seeds.
Metonymy and synecdoche both substitute a closely related word for the word that you'd use when speaking literally. Metonymy uses an attribute that's associated with the subject to describe that subject; for example, whenever you use the term "the crown" to describe royalty or "the cloth" to describe priesthood, you're using metonymy. Synecdoche, which is closely related to metonymy, uses part of something as a symbol for the whole; "all hands on deck" is a well-used example.