letter, missive

a written message addressed to a person or organization; "mailed an indignant letter to the editor"

• business letter — a letter dealing with business
• covering letter, cover letter — a letter sent along with other documents to provide additional information
• crank letter — a hostile (usually anonymous) letter
• encyclical, encyclical letter — a letter from the pope sent to all Roman Catholic bishops throughout the world
• personal letter — a letter dealing with personal affairs
• form letter — a letter that is printed in multiple copies and mailed to a list of recipients
• open letter — a letter of protest; addressed to one person but intended for the general public
• chain letter — a letter that is sent successively to several people
• pastoral — a letter from a pastor to the congregation
• round robin — a letter signed by a number of people
• airmail letter, air letter, aerogram, aerogramme — a letter sent by air mail
• epistle — especially a long, formal letter
• dead letter — a letter that can neither be delivered nor returned
• letter of intent — any letter expressing an intention to take (or forgo) some action
• invitation — a request (spoken or written) to participate or be present or take part in something

• document — anything serving as a representation of a person's thinking by means of symbolic marks
• text, textual matter — the words of something written

• postscript, PS — a note appended to a letter after the signature
• address, destination, name and address — written directions for finding some location; written on letters or packages that are to be delivered to that location

• mail — the bags of letters and packages that are transported by the postal service
• correspondence — communication by the exchange of letters