A" and "an" are indefinite content articles that precede nouns or even the adjectives modifying nouns. In English grammar, "a" and "an" are determiners, meaning they specify the id or quantity of some thing, and for both words and phrases, that amount is "one"—the term from which They are derived. https://theprettierlife.com/discovering-your-dream-home-with-heather-fabris-real-estate-your-trusted-guide-in-realizing-your-vision/