The smallest number that is a larger magnitude than a trillion (1012) is a quadrillion, which is equal to 1015. A quadrillion is also known as a billiard by its formal European name.
Large numbers in the American number system all typically share the "illion" suffix. The smallest number in this category is a million, which has an "m" prefix. Prefixes come from Latin names of numbers. For example, "bi" is the Latin term for two, and "tri" is the Latin term for three. Billion is consequently the next order of magnitude after million, and trillion comes after billion.