The letter "a" is the first letter and the first vowel of the Latin alphabet, widely used in modern English and many other languages globally. It serves multiple linguistic functions: as a letter representing a vowel sound, as an indefinite article in English ("a man," "a house"), and as a symbol in various contexts such as grading systems (an A grade) or in music (representing the sixth tone of the C-major scale). In written form, it appears in both lowercase "a" and uppercase "A" forms. The letter "a" also has phonetic importance as an open front or central unrounded vowel sound in languages.

Thus, "a" is one of the most fundamental characters in alphabets based on Latin script with broad uses in language, grammar, music, and symbolic representations.