The Bedford Glossary of Critical and Literary Terms - Ross Murfin 2018
Synecdoche: A figure of speech (more specifically a trope) in which a part of something is used to represent the whole or, occasionally, the whole is used to represent a part. In synecdoche, the vehicle (the image used to represent something else) is part of the tenor (the thing being represented) or vice versa. Synecdoche is distinguished from metonymy, a trope in which one thing is represented by another that is commonly and often physically associated with it. Referring to a boat as a “sail” involves synecdoche, whereas referring to a monarch as “the crown” involves metonymy.
EXAMPLES: Examples of synecdoche in which a part represents the whole include referring to a car as “wheels” and to the violins, violas, cellos, and basses in an orchestra as the “strings.” Likewise, in William Shakespeare’s play Romeo and Juliet (1596), Capulet has “two more years” in mind when he hopes that “two more summers” will “wither in their pride” before his daughter Juliet is thought “ripe to be a bride.” The narrator in Elie Wiesel’s autobiographical novel Night (1958), interned in Nazi concentration camps where he is terribly underfed and overworked, speaks of himself as “a body. Perhaps less than that even: a starved stomach.”
Examples of synecdoche in which the whole represents a part include referring to how “life” or “the world” has treated you; speaking of sports teams by their home cities (e.g., “Chicago beat Cleveland in the World Series”); and using “society” to mean “high society,” as in Jane Austen’s Mansfield Park (1814) and many other nineteenth-century novels.