What does the reference line of a letter typically include?

The reference line of a letter typically includes the purpose of the communication, as it acts as a focal point for the recipient to immediately understand the context of the correspondence. This line often provides a brief summary of the letter's intent, making it easier for the reader to grasp the essential message or topic being addressed before delving into the details of the letter.

In a professional letter format, the other components—such as the date of writing, the signature of the sender, and the recipient's address—play different roles. The date informs the reader when the letter was written, the signature authenticates and validates the correspondence, and the recipient's address ensures the correct delivery of the letter. However, none of these elements fulfill the primary function of the reference line, which is to clearly communicate the letter's purpose at a glance. Therefore, the focus on conveying the essence of the communication is why the purpose of the letter is the correct answer regarding the reference line.