It shouldn't. It's an American idiom.
Yes, it is an adjective. It means of or according to the alphabet (sequence of letters used in language).
Informal letter uses a short forms while semi formal use a very limited short forms.
Official letters are more formal written communication used for business. Personal letters are less formal and written between family and friends. The heading, salutation. body, closing and signature are different in each type of letter.
No, it is an adjective (legal, or formal), or a noun (a public authority). It is related to the noun office.
An official letter is written to convey official information and is written in a very formal way. Business letter conveys information of a business type and may not be quite so formal. Business letters can also be used to persuade, while official letters are used only to convey information.
The most formal kind of functional writing would be formal letters. This type of letter would be used in circumstances dealing with business matters or even when writing to a stranger.
It's a formal way of expressing regards, usually used in the beginning of formal "inter-departmental, ministerial, etc." letters. Extend here means give.
The only adverb that appears to be used is changeably, from the adjective changeable.There does not seem to be any formal word changingly.
The proper adjective for Oklahoma is "Oklahoman." This term is used to describe people, things, or attributes related to the state of Oklahoma. It is derived from the name of the state itself and is commonly used in formal and informal contexts to denote a connection to Oklahoma.
A business memo is usually used to communicate with a company or organization. It is less formal than business letters.
Papal bull
Speeches.