How is a metaphor defined?

A metaphor is defined as a figure of speech that makes a direct comparison between two unlike things without using "like" or "as." This allows writers to create vivid imagery and convey deeper meanings by suggesting that one thing is another, thereby illuminating the qualities they share. For instance, saying "Time is a thief" implies that time steals moments from our lives, drawing a strong connection between time and theft to express a more complex idea about the passage of time.

In contrast, the other choices highlight different literary concepts. The use of "like" or "as" describes a simile, not a metaphor. A metaphor does not function primarily as a device for indicating setting, nor is it used specifically for revealing a character's inner thoughts. Metaphors serve a broader purpose in enriching language and enhancing the emotional resonance of a text.