Which of the following best defines a letter?

The correct answer defines a letter as a written communication often sent by mail. This definition captures the essence of what a letter is—a format used to convey messages, thoughts, or information from one person to another in a written form. Letters can be formal or informal and may serve various purposes, including personal correspondence, business communication, or official notifications.

Understanding the characteristics of letters helps emphasize their role in effective communication. While the other options relate to different forms of written or verbal expression, they do not adequately or accurately represent the specific nature of a letter as a distinct form of communication that is typically characterized by being written and often delivered through postal services or other delivery methods. Specifically, a letter usually contains a greeting, body text, and a closing, differentiating it from the other choices provided.