Speaking better English - Synecdoches
What is a synecdoche?
It is a figure of speech in which, most often, a part of something is used to refer to its whole.
Let's have a look at some of these
"The captain commands one hundred sails" Obviously the Captain doesn't actually command one hundred sails, but the sails are part of a ship, so it is a way of saying that the captain commands one hundred ships, the ships being the thing of which a sail is a part of.
Using synecdoche's is a way of making what you are saying more interesting.
If you said "check out my new wheels," "wheels" is another example of synecdoche, used here to refer to a "car." A part of a car, in this example, represents the whole of the car. So we are saying check out my new car. Synecdoche's are often used in speech my people to draw attention to an object. Mostly people use a synecdoche to spice up everyday language.
We can use this example of a car perhaps in a different way As we saw, "wheels" was a synecdoche for "car." Another common word for car is a "ride." so we could say, "Let's take my new ride out for a spin." The car is replaced by the word ride. You ride in a car, so it's a related word, but it's not an element of a car. This looks like a synecdoche but it isn't. Instead this is a metonymy. Whilst a synecdoche takes an element of a word or phrase and uses it to refer to the whole, a metonymy replaces the word or phrase entirely with a related concept. Some synecdoche's are a form of metonymy.
Here are some examples