Letters are what make up the alphabet that we use every day, and this word can also refer to a type of written communication between two or more individuals. There are letters quotes for each of these definition, and Greek letters signify your inclusion into a fraternity or sorority. In the English language there are 26 letters in the alphabet, but other languages may contain less or more. If the word letters is used to refer to written communication then this communication can be informal, between friends and family members, or it can be formal such as a business letter or legal correspondence. Without letters the level of communication that we have would be limited if not impossible, and the human race would still be grunting and making gestures while hiding in caves.