Uppercase letters, also known as capital letters, are larger versions of the alphabet's letters. They are used at the beginning of sentences and for proper nouns, such as names of people, places, and organizations. For example, the letter A is the uppercase form of the lowercase letter a. In the English language, there are 26 uppercase letters, ranging from A to Z. Each letter has a corresponding lowercase version, which is typically used in the middle or at the end of sentences. Uppercase letters help to indicate the start of new ideas and emphasize important words.