1. A written or printed character: This is the most common meaning.
* "The letter 'A' comes before the letter 'B'."
* "He wrote a letter to his friend."
2. A written communication:
* "She received a letter from her grandmother."
* "The postman delivered a letter this morning."
3. A printed or typed character, especially one that is a part of a word or sentence:
* "The letters in the word 'cat' are C, A, and T."
* "I can read letters in different fonts."
4. An official document:
* "She received a letter of recommendation for her job application."
* "The government sent a letter to the people of the city."
So, yes, the word "letter" is a noun with multiple meanings and uses.