The English alphabet has 26 letters; each can be written in both uppercase and lowercase letters, the former known as capital letters and the latter as small letters.
Capital letters are reserved for nouns (names of specific people, places, or things), the first letter of a sentence, and acronyms (words composed from letters from multiple words such as NASA or AIDS). Lowercase letters should be used wherever appropriate.
Upper and lower case letters differ not only in their uses but also in their forms. Capital letters always take the same form regardless of what font or style of writing is being employed, while lower case letters may vary depending on font style used – for instance, in some fonts, “a” is written with a small loop at its top while in others it has an inverted tail at the bottom.
Upper and lowercase letters serve as the building blocks of written language, each possessing its own specific form to distinguish it from others. Furthermore, letters can be combined into words, which in turn form sentences.
Upper and lower case letters serve to represent the sounds of spoken language, as well as serve as building blocks of written language. When you see a word written in upper and lower case letters, you can typically read it out loud aloud.
Upper and lower case letters both play important roles for various reasons. Upper case letters can help emphasize writing in all capital letters for emphasis or formal style writing; lower case letters allow more relaxed or informal styles of writing by using all lowercase letters instead.