Which term describes referring to a whole by one of its parts?

The term that describes referring to a whole by one of its parts is synecdoche. This rhetorical device involves using a specific element of something to represent the entire entity, creating a more vivid or relatable connection for the audience. For example, saying "all hands on deck" uses "hands" to refer to the sailors as a whole, effectively conveying the idea of requiring everyone's participation without explicitly mentioning "sailors."

Synecdoche is distinct from other literary terms such as metonymy, which involves substituting the name of one thing with the name of something closely associated with it, rather than merely a part of the whole. Hyperbole refers to exaggerated statements not meant to be taken literally, and alliteration is the repetition of the same consonant sounds at the beginning of words in a phrase. Each of these terms serves different purposes in language and literature, but in the context of the question, synecdoche is the correct choice for describing the relationship of a part to its whole.