The difference between metonymy and synecdoche can be quite subtle, though it is noteworthy as it involves the relationship between the two objects being discussed. Metonymy is a rhetorical device in which one thing is referred to by using something that is separate but related conceptually. Synecdoche, on the other hand, is a process by which one thing is referred to by using something that is a part of it. The major difference between metonymy and synecdoche is in the relationship between the object or thing that is being referred to and the actual term being used.
Metonymy and synecdoche are closely related and quite similar, and this connection can make it difficult to differentiate between the two. This differentiation may be most easily seen by establishing exactly what each concept means. Metonymy is used to refer to one thing by directly referring to something else that it is associated with, but which it is not actually a part of. This can be seen in settings and terms such as the phrase “Washington” used to refer to politicians who work in Washington, D.C., “the class” used to refer to those students who attend a particular class, and “the crown” used to refer to a monarch or other ruling figure who wears a crown as a symbol of power.
Though metonymy and synecdoche are similar, there is a difference in how each rhetorical phrase is constructed. Synecdoche also uses a related item to refer to something else, but this is typically done by referring to part of something to mean the whole. Labor and workers are often referred to as “hands,” while the term “wheels” can be used to refer to an entire car, and the word “lead” is often used to refer to bullets. In each of these examples, the synecdoche is formed by using something that is a part or component of an item to refer to that entire item.
The difference between metonymy and synecdoche lies in the different relationships between the two items being referred to. In metonymy, these two items are related in some way but one is not directly a part or component of another, which is the case in synecdoche. Both metonymy and synecdoche are so similar, however, that some people may view synecdoche as a very specific type of metonymy. The two ideas are often taught separately and should be considered as two different devices that can be used to build rhetorical connections between related concepts or objects.