what is the major difference between a formal and informal letter.

Answer 1

From Internet:

Formal writing is that form of writing which is used for the business,legal,academic or professional purpose. ...
Formal writing must use a professional tone,whereas a personal and emotional tone can be found in informal writing.
In formal writing,use of slang is not at all common,whereas we normally use slang in informal writing.

Answer 2

At school my aunty asked that question,
A. a boy said is: a formal letter is written to people that we aren't familiar with. informal letter are written to people we know.
B. a boy said it isn't true, he said: a formal letter has two addresses while an informal has one address.
pls which one is true (A ) or( B )

Answer 3

I'd go with A.
B is just strange!