A synecdoche (, sih-NEK-d?-kee; from Greek , synekdoch?, lit. "simultaneous understanding") is a figure of speech in which a term for a part of something refers to the whole of something or vice versa. A synecdoche is a class of metonymy, often by means of either mentioning a part for the whole or conversely the whole for one of its parts. Examples from common English expressions include "suits" (for "businessmen"), "boots" (for "soldiers") (pars pro toto), and "America" (for "the United States of America", totum pro parte).
The use of government buildings to refer to their occupants is metonymy and sometimes also synecdoche. "The Pentagon" for the United States Department of Defense can be considered synecdoche, as the building can be considered part of the department. Likewise, using "Number 10" to mean "the Office of the Prime Minister" (of the United Kingdom) is a synecdoche.
Synecdoche is a rhetorical trope and a type of figurative speech similar to metonymy--a figure of speech that uses a term that denotes one thing to refer to a related thing. Indeed, synecdoche is sometimes considered a subclass of metonymy. It is more distantly related to other figures of speech, such as metaphor.
More rigorously, metonymy and synecdoche can be considered subspecies of metaphor, intending metaphor as a type of conceptual substitution (as Quintilian does in Institutio oratoria Book VIII). In Lanham's Handlist of Rhetorical Terms, the three terms have somewhat restrictive definitions, arguably in tune with a certain interpretation of their etymologies from Greek:
Synecdoche is often used as a type of personification by attaching a human aspect to a nonhuman thing. It is used in reference to political relations, including "having a footing", to mean a country or organization is in a position to act, or "the wrong hands", to describe opposing groups, usually in the context of military power.
The two main types of synecdoche are microcosm and macrocosm. A microcosm uses a part of something to refer to the entirety. An example of this is someone saying that they "need a hand" with a project, when they really need the entire person. A macrocosm is the opposite, using the name of the entire structure of something to refer to a small part. An example of this is saying "the world," when the speaker really means a certain country or part of the world. The figure of speech is divided into the image (what the speaker uses to refer to something) and the subject (what is being referred to).
This type of reference is quite common in politics. The residence of an executive is often credited for the executive's action. A spokesperson of the Executive Office of the President of the United States is identified in "The White House announced a new plan to reduce hunger." References to the King or Queen of the United Kingdom are made in the same fashion by referring to today's official residence, Buckingham Palace. Worldwide examples include "the Sublime Porte" of the Ottoman Empire, and "the Kremlin" of Russia.
Sonnets and other forms of love poetry frequently use synecdoches to characterize the beloved in terms of individual body parts rather than a coherent whole. This practice is especially common in the Petrarchan sonnet, where the idealised beloved is often described part by part, from head to toe.
It is also popular in advertising. Since synecdoche uses a part to represent a whole, its use requires the audience to make associations and "fill in the gaps", engaging with the ad by thinking about the product. Moreover, catching the attention of an audience with advertising is often referred to by advertisers as "getting eyeballs", another synecdoche. Synecdoche is very common in spoken English, especially in reference to sports. The names of cities are used as shorthand for their sports teams to describe events and their outcomes, such as "Denver won Monday's game", when it would be more accurate that a sports team from the city won the game.
Kenneth Burke (1945), an American literary theorist, declared that in rhetoric the four master tropes, or figures of speech, are metaphor, metonymy, synecdoche, and irony. Burke's primary concern with these four master tropes is not simply their figurative usage but their role in the discovery and description of the truth. He described synecdoche as "part of the whole, whole for the part, container for the contained, sign for the thing signified, material for the thing made... cause for the effect, effect for the cause, genus for the species, species for the genus". In addition, Burke suggests that synecdoche patterns can include reversible pairs such as disease-cure. Burke proclaimed the noblest synecdoche is found in the description of "microcosm and macrocosm" since microcosm is related to macrocosm as part to the whole, and either the whole can represent the part or the part can represent the whole". Burke also compared synecdoche with the concept of "representation", especially in the political sense in which elected representatives stand in pars pro toto for their electorate.