The format of writing a Yoruba language letter typically follows these basic guidelines:

1. Write the date at the top of the letter, starting with the day, then the month, and then the year.
2. Write the recipient’s name and address next. This should be written in full, including the town, state, and country where the recipient is located.
3. Begin the letter with a formal greeting. In Yoruba culture, this usually involves using a respectful term such as “E kabo” (welcome) or “Bawoni” (how are you).
4. Start the body of the letter with an introduction that states the purpose of the letter. This could be a simple greeting, or a more detailed explanation of the reason for writing.
5. Use clear and concise language to convey your message. Be respectful, but also be clear about your intentions.
6. Close the letter with a formal ending, such as “E dupe” (thank you), “E se” (please), or “O dabo” (goodbye).
7. Sign the letter with your name and any other relevant information, such as your title or position.

Here is an example of a Yoruba language letter:
Ojo ise yii ni ojo ti mo fi ranse si e
Olorunbe Street, Surulere, Lagos.
Bawoni,
E pele o. Mo ki yin lati fi e sile awon ohun ti o sele ni oja. Mo ma so fun e wipe mo ti mo ohun to n gba soro lati won ni ki won gba lati siwaju ni abule won.
E dupe fun gbogbo ohun to e gba lowo mi.
Oluwaseun.
Translation:
Today is the day I am writing to you.
Olorunbe Street, Surulere, Lagos.
Hello,
Greetings. I am writing to inform you about the things that have been happening in the market. I want to let you know that I have spoken with them to move forward in their village.
Thank you for everything you have done for me.
Oluwaseun.