Metonomy in English Literature

Greek word "Metonomy" means "a change of name". In metonomy the name of one thing is substituted for that of another with which it is closely associated. The association of one thing with another is so deep that whenever we think of one thing we can remember, the other which is substituted by former. For example-
"The crown is used to mean monarchy or when we think of the 'pen' we think of the writer. Thus 'Fear not' we are loyal to the throne".
In these sentences the throne is not physically a part of the king, the idea of kingship is closely associated and throne is used as the substituted of the king. So it is the metonomy.

Symbol in English Literature

A symbol is something which represents something else, often an idea or quality, by analogy. It may be conventional, private or extended. White, Lion, and rose commonly symbolize innocence, courage, and beauty. Such symbols exist by convention and tradition. A snake may stand for evil or wisdom, according to different conventions. Writers either use these conventional symbols or invent their own which are private symbols. Blake and Shelley, use both conventional and private symbols in their poetry. However, novelists also use symbols.

A symbol may be seen as a species of metaphor in which the exact subject is not explicit and may even be mysterious. A whole poem may be a symbol of this kind. Blake's The Stick Rose" is typical. Blake's children in his poems are symbol of innocence, Shelley's "West Wind" is a symbol of destroyer and preserver.

Allegory in English Literature

Allegory has been derived from a Greek term "allos" meaning "disguise". So allegory suggests to describe a thing under disguise of another thing. It is an extended narrative in prose or poetry that delineates a story which has an inner meaning.

We can distinguish two main types: Historical and Political allegory, in which the characters and actions represent, or allegorize historical events, and the other one is, the Allegory of ideas, in which the literal characters represent abstract concepts and the plot exemplifies a doctrine or thesis. Another type of allegory symbolizes any religious issue. For example, Coleridge's "The Rime of the Ancient Mariner" is a Christian allegory of guilt and redemption.

John Keats makes a subtle use of allegory throughout his ode, "To Autumn", most explicitly in the second stanza, which represents autumn personified as a female figure and the scenes and the activities of the harvest season. Thus, allegory is a powerful literary figure of speech used by the skillful writer to give a moral, religious, or satirical meaning.