Art music (also known as Western classical music, cultivated music, serious music, canonic music, or more flippantly, "real music" and "normal music") is an umbrella term that refers to musical traditions, implying advanced structural and theoretical considerations and a written musical tradition. The main tradition in the Western world is usually called classical music. "Serious" or "cultivated" music are terms frequently used as a contrast for ordinary, everyday music (popular and folk music, also called "vernacular music"). After the 20th century, art music was divided into two extensions: "serious music" and "light music".