Definition of letter :
1. A letter; an epistle.
2. A mark or character used as the representative of a sound, or of an articulation of the human organs of speech; a first element of written language.
3. A single type; type, collectively; a style of type.
4. A telegram longer than an ordinary message sent at rates lower than the standard message rate in consideration of its being sent and delivered subject to priority in service of regular messages. Such telegrams are called by the Western Union Company day, / night, letters according to the time of sending, and by The Postal Telegraph Company day, / night, lettergrams.
5. A writing; an inscription.
6. A written or printed communication; a message expressed in intelligible characters on something adapted to conveyance, as paper, parchment, etc.; an epistle.
7. Learning; erudition; as, a man of letters.
8. One who lets or permits; one who lets anything for hire.
9. One who retards or hinders.
10. To impress with letters; to mark with letters or words; as, a book gilt and lettered.
11. Verbal expression; literal statement or meaning; exact signification or requirement.
crown, alphabetical, billet-doux, just as directed, button, chevron, memorandum, cap, circular, sweep, word, yellow ribbon, alphabetize, capital, award, walk off with, chain letter, take, words, precisely, billet, perfectly, air letter, recapture, dead letter, cover letter, ligature, carry off, report, varsity letter, armband, ribbon, stripe, insignia, exactly, block capitals, initial, block letters, alphabetic character, minuscule, letter of the alphabet, Dear John letter, badge, walk away with, missive, enclosure
correspondence (part of speech: noun)
letter (part of speech: noun)