Final answer:
The extra part is the inside address, which comprises the recipient's name, title, and organizational address. The inside address is included as part of the six main parts of a business letter, which also includes the heading, salutation, body, closing, and the writer's signature with their typed name.
Step-by-step explanation:
The extra part of a business letter that differentiates it from a friendly letter is the inside address. This section includes the name of the person you are writing to, their title, and the full address of the organization. The six main parts of a business letter are:
- Heading (Your return address and the date)
- The inside address (Recipient's name and address)
- Salutation (Formal greeting)
- Body (The content of your letter)
- Closing (A formal ending to the letter)
- Your signature followed by your typed name
In a business letter, everything should be left-justified and single-spaced, with double spacing between paragraphs. Using a professional font like Times New Roman or Arial in size 11-12 is recommended for readability. Moreover, all business letters should start with a polite opening, state the purpose concisely, and have a formal closing, typically 'Sincerely' or 'Thank you.'