let·ter
n.
1. A written symbol or character representing a speech sound and being a component of an alphabet.
2. A written symbol or character used in the graphemic representation of a word, such as the h in Thames. See note at Thames.
3. A written or printed communication directed to a person or organization.
4. A certified document granting rights to its bearer. Often used in the plural.
5. Literal meaning: had to adhere to the letter of the law.

i got it..