Synecdoche is closely related to metonymy—a figure of speech in which a term that denotes one thing is used 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 sub-species 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:
metaphor: changing a word from its literal meaning to one not properly applicable but analogous to it; assertion of identity rather than, as with simile, likeness.
metonymy: substitution of cause for effect, proper name for one of its qualities, etc.
The word "synecdoche" is derived from the Greek word συνεκδοχή = "together-out-accepting", from the prepositions συν- + εκ- and the verb δέχομαι (= "I accept"), originally meaning accepting a part as responsible for the whole, or vice versa.
Synecdoche can be used to emphasize an important aspect of a fictional character; for example, the X-Files character the Smoking Man. 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.
He defined 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…". Burke's definition provides examples of relationships of convertibility. 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 suggested that the word synecdoche can be substituted for the word representation. For example, Burke presented synecdoche in a political realm. In some forms of government one is elected from a social body to represent the entirety of that specific social body. Therefore, this form of government displays a synecdoche relationship since it includes a form of representation, i.e. a part of the whole.
A part referring to the whole
Referring to people according to a single characteristic: "the gray beard" representing an older man or "the long hair" representing a hippie. This leads to bahuvrihi compounds.
Describing a complete vehicle as "wheels", or a motorcycle as handlebars
Referring to people by a particular body part. For example, "head count", "counting noses", or "all hands on deck!", or "eyeballs" observing adverts
In Wordsworth's "We Are Seven", the speaker says, "Your limbs they are alive" (l. 34). "Limbs" represent the entire body, so the narrator is trying to explain to the little girl that she is alive and breathing, unlike her two dead siblings.
In Coleridge's "Frost at Midnight", the speaker says "…or the redbreast sit and sing/ Betwixt the tufts of snow…" (l. 67-8). This phrase symbolizes the coming of spring, as robins are referred to as harbingers of spring.
A general class name used to denote a specific member of that or an associated class
"the good book", or "The Book" for the Bible ("Bible" itself comes from the Greek for "book")
"truck" for any four-wheel drive vehicle (as well as long-haul trailers, etc.)
"He's good people". (Here, the word "people" is used to denote a specific instance of people, i.e., a person. So the sentence would be interpreted as "He's a good person".)
A specific class name that refers to a general set of associated things
^Lanham, Richard A (1991). A Handlist of Rhetorical Terms: A Guide for Students of English Literature, Second Edition. Berkeley/Los Angeles/London: California University Press. p. 189. ISBN0-520-07669-9.
^ abBurke, Kenneth (1945). A Grammar of Motives. New York: Prentice Hall. p. 503.
^Burke, Kenneth (1945). A Grammar of Motives. New York: Prentice Hall. pp. 507–508.
^ abBurke, Kenneth (1945). A Grammar of Motives. New York: Prentice Hall. p. 508.
^ abStephen Greenblatt et al. The Norton Anthology of English Literature, volume D, 9th edition (Norton, 2012)