Which device uses an informal word choice instead of a formal one, such as "lend me your ears"?

The correct answer reflects the use of an informal word choice, which can evoke familiarity and a conversational tone. When someone employs words like "lend me your ears," they are using a more casual or figurative expression rather than a literal or formal one.

The term “metonymy” refers to a figure of speech where one word or phrase is substituted for another with which it is closely associated. In this case, "ears" stands in for listening or attention, creating a vivid image that resonates well within speech or writing. Such informal expressions help to create a connection with the audience.

Other options do not fit this definition. "Colloquy" refers to a formal conversation or dialogue, which does not emphasize informal word choice. "Synecdoche" involves a part representing a whole, which does not specifically address the informal tone. "Apostrophe" is a rhetorical device where the speaker addresses an absent or imaginary person or a personified abstraction, but it does not inherently involve an informal word choice. Each of these options serves a different function in language, but metonymy is the one that captures the essence of using a more casual style effectively.