A bank bill, also known as a banknote or currency note, is a piece of paper money issued by a country's central bank. There are several synonyms for bank bill depending on the region or country. In the United Kingdom, it is referred to as a "note" or "banknote." In the United States, it is commonly called a "dollar bill," while in Canada, it is referred to as a "loonie" or "toonie." In Australia, it is known as a "dollar note," and in New Zealand, it is called a "banknote." Regardless of the synonym used, bank bills serve as a vital medium of exchange in an economy and are an essential component of monetary policy.