On Synecdoche and Metonymy
The terms metonymy and synecdoche refer to two similar figures of speech used as rhetorical devices. (They're easy to confuse, so feel free to read this as many times as you need.)
Synecdoche refers to the practice of using a part of something to stand in for the whole thing. Two common examples from slang are the use of wheels to refer to an automobile (“she showed off her new wheels”) or threads to refer to clothing.
A classic example of synecdoche is the use of the term hands to mean “workers” (as in “all hands on deck”), or the noun sails to mean “ships.” Synecdoche is also sometimes used in the names of sports teams (the White Sox, the Blue Jackets).
Metonymy refers to the use of the name of one thing to represent something related to it, such as crown to represent “king or queen” or White House or Oval Office to represent “President.” When you say “a bunch of suits were in the elevator” when you are talking about businesspeople, that is an example of metonymy, because you're using the common wardrobe of executives as shorthand for people in that occupation.
It’s metonymy when you use a person’s name to refer to the works by that person, as when you say “I had to read Hemingway for a class” when you really mean “I had to read a work by Hemingway for a class.” Another straightforward example is when you use a city’s name to refer to its team, as when you say “Houston was ahead by six points.”
Some examples are so common as to become a regular part of the lexicon. For example, the use of press to mean “journalists” dates to the 17th century and occurs in the First Amendment (“Congress shall make no law … abridging the freedom of speech, or of the press…”). This use, of course, attributes journalists with the name of the device used for printing newspapers and other circulations.
In similar classic examples of metonymy, an occupation is identified by the tools used to carry it out. A sportswriter might say that a team’s bats went into a slump, when the writer really means that the hitters in the lineup went into the slump. Sometimes metonymy is used to make a name catchier than the item it replaces, like when surf and turf, using two rhyming terms that allude to the sea and land, is used for to a dish combining seafood and beef.
Like many terms used in rhetoric, both synecdoche and metonymy derive from Greek. The syn- in synecdoche means "with, along with" (much like as in synonym) and ekdochē means "sense, interpretation." Metonymy meanwhile, combines the Greek meta (“among, with, after,” the same root found in metaphor) with onyma, meaning “name” or “word.”
Now that you've got these two figured out, we hope you enjoy reading the rest of Merriam-Webster.