IELTS books and teachers sometimes talk about formal, semi-formal, and informal letters. But a student asked me an interesting question recently:
Can we make things easier by forgetting about "semi-formal"?
Actually, I think the answer is yes! When writing to a colleague or neighbour, you can write in a friendly, informal way using the informal features mentioned in this lesson. I can't really think of any reason why we need the "semi-formal" category for IELTS writing purposes. Your letter will be either formal or friendly!
Feel free to disagree with me if you can find a reason why we need the semi-formal category. Maybe I've missed something.