1 [count] : any one of the marks that are symbols for speech sounds in written language and that form an alphabet
▪ the letter “a” ▪ “F” is the sixth letter of the English alphabet. ▪ I wrote my name in capital letters. 2 [count] : a written or printed message to someone
▪ write/send/mail a business/love letter to someone ▪ letters to the editor ▪ They always answer the letters they get/receive from their fans. ▪ He asked them for a letter of recommendation/introduction. — see picture at mail; see also chain letter, cover letter, dead letter, form letter, newsletter, open letter, poison-pen letter 3 letters [plural] formal : literature
▪ She's well-known in the field of English letters. — see also man of letters 4 [singular] : the exact meaning of something (such as a law) that is stated in writing
▪ They seem to be more concerned with obeying the letter of the law [=with doing exactly what the law says] than with understanding the spirit of the law. 5 [count] US : a large cloth letter that is the first letter of a school's name, that is awarded to a student for playing on a sports team, and that can be sewn onto a sweater or jacket
▪ He earned his letter in football.