What is the term for using language effectively to please or persuade?

The term for using language effectively to please or persuade is "rhetoric." Rhetoric refers specifically to the art of persuasive speaking or writing. It involves employing various techniques and strategies to influence an audience, appeal to emotions, and convey arguments convincingly. By mastering rhetoric, individuals can enhance their ability to communicate ideas and persuade others in various contexts, such as speeches, debates, and written works.

Other terms presented do not capture the essence of persuasive language. For instance, "sanction" generally refers to a penalty for disobeying a law or a rule or can mean official approval, which does not pertain to the art of effective language use. "Soliloquy" is a dramatic monologue that expresses a character's thoughts spoken aloud when they are alone, not aimed at persuasion but rather at revealing inner feelings. "Platitude" refers to a statement that is overused and lacks originality or depth, which does not align with the notion of skillfully using language to persuade. Thus, "rhetoric" is the most appropriate choice for this concept.