The term BUS. CARD DATUM is composed of three words: Bus, Card, and Datum. Bus refers to a large motor vehicle used for transporting passengers, Card is a thin, flat piece of stiff paper or plastic used for various purposes, and Datum is a single piece of information. Together, these three words refer to a type of electronic ticketing system used on public transportation, such as buses, which stores information about the user's travel history and payment information on a card.