Synecdoche; from Greek synekdoche (συνεκδοχή), meaning "simultaneous understanding") is a figure of speech in which a term is used in one of the following ways:

Part of something is used to refer to the whole thing (Pars pro toto), or

A thing (a "whole") is used to refer to part of it (Totum pro parte), or

A specific class of thing is used to refer to a larger, more general class, or

A general class of thing is used to refer to a smaller, more specific class, or

A material is used to refer to an object composed of that material, or

A container is used to refer to its contents.