Definition of "Letter" :
noun: a written message addressed to a person or organization
"Mailed an indignant letter to the editor."
noun: an award earned by participation in a school sport
"He won letters in three sports."
noun: the conventional characters of the alphabet used to represent speech
"His grandmother taught him his letters."
noun: a strictly literal interpretation (as distinct from the intention)
"He followed instructions to the letter."
noun: owner who lets another person use something (housing usually) for hire
verb: mark letters on or mark with letters
verb: set down or print with letters
verb: win an athletic letter