An extended metaphor, also known as a conceit or sustained metaphor, is when an author exploits a single metaphor or analogy at length through multiple linked vehicles, tenors,and grounds. Tenor is the subject of the metaphor, vehicle is the image or subject that carries the weight of the comparison, and ground is the shared proprieties of the two compared subjects. Another way to think of extended metaphors is in terms of implications of a base metaphor. These implications are repeatedly emphasized, discovered, rediscovered, and progressed in new ways.
Symbolism is a common theme of extended metaphors. This is often seen in William Shakespeare's work. For example, in Sonnet 18 the speaker offers an extended metaphor which compares his love to Summer. Shakespeare also makes use of extended metaphors in Romeo and Juliet, most notably in the balcony scene where Romeo offers an extended metaphor comparing Juliet to the sun. An excerpt is provided below:
This poem can only be understood if the reader has knowledge of the “life-is-a-journey” metaphor. That knowledge includes understanding of other grounds between the tenor (life) and vehicle (journey) that are not as transparent in this poem. Holyoak (2005) gives examples of these grounds, “person is a traveler, purposes are destinations, actions are routes, difficulties in life are impediments to travel, counselors are guides, and progress is the distance traveled.”
In "The Thought-Fox", Ted Hughes uses the extended metaphor that the idea he struggles to find is actually a fox. By using an extended metaphor, it becomes more convincing.