letter (n.1)

c. 1200, "graphic symbol, alphabetic sign, written character conveying information about sound in speech," from Old French letre "character, letter; missive, note," in plural, "literature, writing, learning" (10c., Modern French lettre), from Latin littera (also litera) "letter of the alphabet," also "an epistle, writing, document; literature, great books; science, learning;" a word of uncertain origin.

According to Watkins, perhaps via Etruscan from Greek diphthera "tablet" (with change of d- to l- as in lachrymose), from a hypothetical root *deph- "to stamp." In this sense it replaced Old English bocstæf, literally "book staff" (compare German Buchstabe "letter, character," from Old High German buohstab, from Proto-Germanic *bok-staba-m).

Latin littera also meant "a writing, document, record," and in plural litteræ "a letter, epistle, missive communication in writing," a sense passed through French and attested in English letter since early 13c. (replacing Old English ærendgewrit "written message," literally "errand-writing"). The Latin plural also meant "literature, books," and figuratively "learning, liberal education, schooling" (see letters).

The custom of giving the school letter as an achievement award in sports, attested by 1908, is said to have originated with University of Chicago football coach Amos Alonzo Stagg. Earlier in reference to colleges it meant "university degree or honor that adds initials to a name" (1888). Expression to the letter "precisely" is from 1520s (earlier after the letter, mid-14c.). Letter-quality (adj.) "suitable for (business) letters" is from 1977. For letters patent (with French word order) see patent (n.).

letter (v.)

"write in letters," 1660s, from letter (n.1). Earlier it was used in a now obsolete sense "instruct" (mid-15c.). Related: Lettered; lettering.

letter (n.2)

"one who lets" in any sense, c. 1400, agent noun from let (v.).

Definitions of letter
letter (n.)
a written message addressed to a person or organization;
mailed an indignant letter to the editor
Synonyms: missive
letter (n.)
the conventional characters of the alphabet used to represent speech;
his grandmother taught him his letters
Synonyms: letter of the alphabet / alphabetic character
letter (n.)
owner who lets another person use something (housing usually) for hire;
letter (n.)
a strictly literal interpretation (as distinct from the intention);
he followed instructions to the letter
he obeyed the letter of the law
letter (n.)
an award earned by participation in a school sport;
he won letters in three sports
Synonyms: varsity letter
letter (v.)
win an athletic letter;
letter (v.)
set down or print with letters;
letter (v.)
mark letters on or mark with letters;