Letters are of several different kinds, and each has its own over-all rules for content and style

Personal letters

Personal letters are those that concern the writer as an individual person, not as an officer in an organization, a seller or purchaser, a client or a dispenser of professional services. Personal letters range in formality from intimate to very formal, since people have relationships of many kinds in their lives.

Intimate letters do not follow ordinary rules, since they are the expression of private thoughts and feelings between people who are closely related in life. Just as people who are limited who are intimate with each other don’t pay a great deal of attention to formal rules of etiquette, intimate letters are not bound by many rules. In general, an intimate letter can contain anything that would be said in conversation by the writer to the addressee.

Letters dealing with personal matters that are exchanged between people not intimately related in life might be called social letters. These letters vary in formality. Since some personal relationships are less formal than others. In social letters, attention must be paid to the rules of polite conversation, and the writer must be careful to make appearance of his letter conform to certain standards. Some social communications, which we will call formal letters, are so stereotyped that they follow very rigid rules in their wording format. Examples are invitations to important social affairs and formal weddings. They may be handwritten, but most often they are printed or engraved in a number of copies and sent out to many people at a time.

Business letters

Business letters make up by far the larger pat of the letters written and mailed today. These letters deal with matters of an impersonal, official, or public nature, as contrasted with personal letters, which deal with private matters. The writer and addressee of a business letter may or may not know each other socially; this fact is irrelevant, since matter being discussed is presumably not affected by relationship. Business letters are quite often written to persons with whom the writer is not acquainted at all, even by name, and with whom he has no need or desire to become acquainted.

Business letters are of many different kinds, and their level of formality varies according to the particular circumstances and the type of relationship that exist between the writer and the addressee. (They could be brothers, for instance, writing about the sale of a piece of property; or they might be total strangers, like a member of the public writing to a government official.) However, they all have in common an objective quality that is lacking in personal letters: their purpose is to get or give information, to obtain something that one wants from someone else, to persuade or to negotiate.

A business letter may be private or official. In a private business letter, the writer is speaking for himself or on his own behalf. ( An example of this type of letter would be one written to one’s personal lawyer.) In official business or some other kind of organization; usually, he does not speak on his own behalf but on behalf of the organization he represent, in official correspondence he is more likely to say “we” or “us”.

When business letters are exchanged between people who know each other personally, the language often becomes a great deal less formal than in ordinary business letters, and occasional personal remarks are included, like “regards to your wife,” or “I hope your cold is better.” These touches, however, do not negate the impersonal nature of the communication; they are just bits of courtesy such as would be said in face-to-face business conference
Other than the variations on formality just mentioned, business letters vary little except in the content-the substance of the letter, the matter being discussed.