Synecdoche and Metonomy
If you are a "little" confused by these two figures of speech, this is the flip for you.
First, let me reassure you; many people find these two devices confusing; however, you are not doomed-- MAZ is here.
Step one---let's review the definitions.
Synecdoche--a figure of speech in which a term for a part of something refers to the whole of something. or vice versa
Now let's look at it this way: part represents whole
whole represents part
Metonomy---a figure of speech in which a thing or a concept is referred to by something with which it is closely associated
Notice, the two things associated are NOT parts of the same thing.