A metaphor is a figure of speech that identifies one thing as being the same as some unrelated other thing, thus strongly implying the similarities between the two. It is therefore considered more rhetorically powerful than a simile. While a simile compares two items, a metaphor directly equates them, and so does not apply any words of comparison, such as "like" or "as." Metaphor is a type of analogy and is closely related to other rhetorical figures of speech that achieve their effects via association, comparison or resemblance including allegory, hyperbole, and simile.One of the most prominent examples of a metaphor in English literature is the All the world's a stage monologue from As You Like It:All the world's a stage, And all the men and women merely players; They have their exits and their entrances; —William Shakespeare, As You Like It, 2/7This quotation contains a metaphor because the world is not literally a stage. By figuratively asserting that the world is a stage, Shakespeare uses the points of comparison between the world and a stage to convey an understanding about the mechanics of the world and the lives of the people within it.The Philosophy of Rhetoric (1937) by I. A. Richards describes a metaphor as having two parts: the tenor and the vehicle. The tenor is the subject to which attributes are ascribed. The vehicle is the object whose attributes are borrowed. In the previous example, "the world" is compared to a stage, describing it with the attributes of "the stage"; "the world" is the tenor, and "a stage" is the vehicle; "men and women" is the secondary tenor, and "players" is the secondary vehicle.Other writers employ the general terms ground and figure to denote the tenor and the vehicle. In cognitive linguistics, the terms target and source are used respectively.