Metonymy, pronounced 'mi-tonn-ə-mee'
is a figure of speech in which a thing or concept is called by the
name of something associated in meaning with that thing or concept,
rather than by its own name. The words "metonymy" and "metonym" come
from the Greek: metōnymía, 'a change of name'.
Metonymy and related figures of speech are common in everyday talk
and writing. Synecdoche is a specific type of metonymy. Synecdoche
refers to a thing by the name of one of its parts. For example,
calling a car “a wheel” is a synecdoche. A part of a car, the wheel
stands for the whole car.
One of the main purposes of using a metonymy is to add flavor to the
writing. The name of a sports team can be used in place of its
individual members.
Other examples: "Wall Street" is often used metonymously to describe
the US financial and corporate sector, and "Hollywood" used as a
metonym for the US film industry. The national capital is often used
to represent the government or monarchy of a country, such as
"Washington" for United States government or "Downing Street" for
the Government of the United Kingdom.
Other metonymys - Crown. (For the power of a king.)
The White House. (the American administration.)
Dish. (To refer an entire plate of food.)
And finally, the old adage, 'the pen is mightier than the sword'
Pen. (For the written word.) Sword - (For military force.)