In language, a metaphor is defined as a direct comparison between two or more seemingly unrelated subjects and mainly uses "is a" to join the first subjects. A metaphor is commonly confused with a simile which compares two subjects using "like" or "as". An example of a simile: "He was as sly as a wolf." In the simplest case, a metaphor takes the form: "The (first subject) is a (second subject)." More generally, a metaphor casts a first subject as being or equal to a second subject in some way. Thus, the first subject can be economically described because implicit and explicit attributes from the second subject are used to enhance the description of the first. This device is known for usage in literature, especially in poetry, where with few words, emotions and associations from one context are associated with objects and entities in a different context.