1.
Formal. A letter used in professional and official contexts
2.
Informal. A type of letter sent to friends or family
3.
Business. A letter used in a work or business setting
4.
Complaint.A letter expressing dissatisfaction with a product or service
5.
Invitation. A letter requesting someone's presence at an event
6.
Apology. A letter written to express regret for a mistake or misunderstanding
7.
Resignation. A letter sent to quit a job or position
8.
Recommendation. A letter written to suggest someone for a job or position
9.
Congratulation. A letter sent to praise someone's achievement or success
